Atlantis. Across two universes, it's the most highly advanced nation on the planet, a submerged society of technology and magic. The people of Atlantis are ruled by a king.
In The Beginning:
Aquaman was not the king of the seas, nor was he Arthur Curry. He was the son of an unnamed undersea explorer who found the lost(and empty) city of Atlantis. This explorer created a study for himself in an air cavern where he trained his son to survive underwater indefinitely using "a hundred different scientific secrets". Named Aquaman by his father, the son went out into the world using his superhuman strength and ability to talk with sea creatures to fight Nazis and other 1940's threats.
It wasn't until the Silver Age, that the seeds of the current origin of Aquaman started, where he was the son of Tom Curry, a lighthouse keeper who fell in love with Atlanna, an exiled Atlantean. Later it would be changed so that Queen Atlanna* and a sorcerer named Atlan* had a child named Orin, who was deemed to carry the Mark of Kordax(which is apparently blond hair) and was cast into the ocean wilds. Orin was found by Arthur Curry, who named the sea child after himself. Arthur Curry/Orin had the same abilities of the Golden Age Aquaman, mostly, except his communication with sea creatures was now telepathic and he could only stay out of water for an hour at a time or start to weaken.
Aquaman became a prominent superhero and a founding member of the Justice League of America, which he would remain a member for extended periods of time. He had two sidekicks Garth who went by Aqualad and Tula who went by Aquagirl, and married Mera, a water-breathing Queen from another dimension.
Aquaman made a career out of defending the seas against such threats as Black Manta(he of the tacky helmet and delusions of grandeur), the Fisherman, the Scavenger, the Human Flying Fish, and his half-brother(the son of Arthur Curry and a human woman) Orm, the Ocean Master. At first light-hearted, his adventures became decidedly darker after the death of his son, Arthur Jr., by Black Manta. The tragedy created a rift between Aquaman and Mera, as well as between Aquaman and Aqualad, who were forced to fight to death by Black Manta for Arthur Jr.'s life. From then on, Aquaman mostly worked alone fending off threats to his throne and trying to patch up his marriage.
In the nineties, a effort was made to update Aquaman for an audience who mainly made light of him. His hand was eaten by angry piranha and was replaced by a harpoon, then a magical one with many capabilities. Also, Aquaman was now more arrogant than before, quick to posture as though he were prepped to be king from birth, as opposed to finding out when he was an adult.
During Our Worlds At War, Aquaman used Poseidon's(or Neptune's) Trident to fight off an Imperiex drone, while Garth, now going by Tempest and with sorcery training from Atlan, tried to temporarily shunt Atlantis into another dimension to prevent it from destruction. He was believed killed in the fight, but really Aquaman and Atlantis were sent into the past were it caused the original Atlantis to sink. In the past, Aquaman's spirit was trapped in the ocean and the Atlanteans were subjugated by ancient Atlantean wizards. It took the Justice League in the past and present to bring Aquaman and Atlantis back to the present, but magic became the order of the day. Wizards took control of Atlantis, imprisoning Mera in a magical haze and making Aquaman public enemy number one.
Banned from the ocean, Aquaman was chosen by the Lady of the Water to become the Waterbearer and wield a water hand that was connected a mystical life river. It didn't take long before Aquaman took on a more traditional look and returning to combating non-mystical threats. He had to deal with the sinking of San Diego and dealing with the survivors who were given water breathing capability. In this new Sub Diego, Aquaman found a new Aquagirl and had a run-in with Black Manta before he tried raising Sub Diego and returning the people back to their natural state. This changed him drastically, and leaving the Aquaman mantle open to a Arthur Joseph Curry, who is apparently the genetically altered clone of the son of a marine scientist.
Namor McKenzie was born to the Atlantean princess Fen and the American captain of the Orcale Leonard McKenzie. Fen went missing from Atlantis and was found by McKenzie while at sea. The two fell in love, but were torn apart when Fen's father Emperor Thakorr sent troops to find Fen. The troops believed Fen was being held captive so they destroyed the Oracle and nearly killed McKenzie bringing Fen back. Back in Atlantis, Fen gave birth a pink-skinned baby boy in the blue-skinned society of Atlantis. He was named Namor, Atlantean for "Avenging Son."
Namor is a mutant, born with small wings on his ankles that gave him flight, superhuman strength, speed and endurance, the ability to copy the abilities of sealife, to communicate telepathically with sealife, and has an extremely long lifespan, seeing as he's not aged much in 60 years. The sealife abilities and lifespan were revealed after the character was revived in the 50's and 60's, but his wings are vintage.
Namor began his adventures as the Sub-Mariner attacking surface dwellers who he felt threatened Atlantis and sealife in general. Eventually, he put aside his anger and joined with the Allies to stop the Axis Powers. He teamed up with Captain America, Bucky, Whizzer, Miss America, the original Human Torch and Toro to form the All-Winners Squad. Wait...in the retconned continuity, Sub-Mariner joined Cap, Buck, Torch and Toro as the Invaders and formed the All-Winners Squad when the Invaders and the Liberty Legion joined together after World War II. Namor was joined by his cousin Aquaria Nautica Neptunia, a human/Atlantean hybrid mutant like himself, who was nicknamed "Namora("Avenging Daughter" in Atlantean)" for her royal cousin. She fully accepted the name after her father was killed by human treasure hunters.
Namor was injured sometime after the War and drifted around as a derelict named Macin. He was found by the Human Torch of the Fantastic Four who recognized Macin for who he was and helped revive his memories. Shortly thereafter, Namor went to find his people, but they had relocated when the original Atlantis was damaged by nuclear testing. Enraged, Namor attacked the surface world repeatedly, being thwarted by the Fantastic Four and the Avengers, before he found the new Atlantis and abandoned his vengeance. In his travels to find Atlantis, he came upon an Arctic tribe worshipping a man encased in ice, so he took the frozen idol and tossed it into the sea. The frozen man was found by the Avengers and revealed to be Captain America.
In his fights with the Fantastic Four, Namor became infatuated with Susan Storm and tried many times to win her affections. One time he used lost gold to buy a production company and offered the Fantastic Four a movie deal in a rather complicated attempt to get Susan's attentions. He stopped actively trying to woo Susan when she married Reed Richards, but still loves her to this day. He married his cousin Lady Dorma, but she was kidnapped and replaced by Llyra of Lemuria in an effort to take control of Atlantis. The plan was stopped, but Lady Dorma was killed.
Though still king of Atlantis, Namor joined(was forced) the Defenders for a time, before gaining his freedom from the group. After a coup forced Namor out of power, Namor joined the Avengers and met his second wife Marrina, an alien aquatic of the Plodex race. The two founded a society of peaceful Atlanteans, but Marrina's evil side emerged and in a battle with the Avengers, she was thought killed. Actually in a coma, Marrina was nevertheless never reunited with Namor. Namor restored order in Atlantis after Atlantis Attacks, but was presumed deceased. He used the anonymity and more undersea treasures to start Oracle, Inc., which he used to fund environment saving programs. He also reconnected with his "cousin" Namorita, a clone of Namora who was passed off as Namora's daughter due to Atlantean taboo against cloning. Namora was poisoned by Llyra and thought deceased, but was recently discovered to be in suspended animation.
Continuing in his habit of discovering lost heroes, Namor went to K'un L'un where he found Iron Fist who was thought deceased. Namor fought against a sorcerer named Master Khan around this time, losing his memory for a short period before finally defeating him. Namor was killed fighting against another sorcerer named Suma-Ket, but was returned to life by the God Neptune. He returned to power as king of Atlantis and head of Oracle, Inc., but sold off the company to focus on Atlantean matters.
Most recently, Namor helped out the modern incarnation of the Invaders and was one of the members of the Illuminati, a council of prominent superheroes who met to decide major issues such what to do about the threat of the Skrulls and how to deal with the Infinity Gauntlet. e broke with the group when it was decided that Bruce Banner, the Hulk, should be sent into deep space to an uninhabited planet. Namor predicted that Hulk would return, angrier than ever, hell bent on revenge. He was proven right. He backed Captain America in the Civil War, after taking custody of Nitro for killing Namorita. His placing of Atlantean spies in America has him in hot water, since a rogue group of Atlanteans are committing terrorist acts in America.
So who wins:
I should start off by saying I'm not one of those people who see Aquaman as a joke. True, he's not my favorite hero, but I could see his place in the DCU and how his powers can be useful in non-water based situations.
That being said, the only time I was really interested in Aquaman's adventures was during the Sub Diego situation, when he was brought back to full-on superhero mode. Before, it seemed to be Aquaman's solo adventures were him fending off usurpers, like all the time. I think there was an issue of the 90's Aquaman where an oil spill had something to do with Kordax or aliens trying to take control of Atlantis. If you wanted Aquaman saving human beings(not to be prejudiced against homo mermanus), you had to read Justice League books. When I found out about the Golden Age Aquaman, I felt kind of gypped for the past couple of decades.
Sub-Mariner, on the other hand, was never meant to be the usual kind of hero. He started off a angry young man, throwing sea slang, and became the arrogant monarch who occasionally worked with the surface dwellers. His appeal is his arrogance and the fact that he has the power to back it up. He was the first anti-hero, the template for every hero who more than likely would choose not to be there. The fact that he was able to keep his personality mostly intact, sans the slang, over the years shows how well he was received with every appearance. No one seemed to feel the need to revamp the character as much as Aquaman was. Aquaman's modern era arrogance seemed to reflect a need to justify Aquaman's place in the Justice League, hell, comics in general.
Sub-Mariner doesn't need jusification and is liked without irony. DC has even tried to have their own Namor, and I don't mean Arthur. He is understandable, preventing the wild characterizations(unless Meltzer starts writing Marvel) that comes from a writer trying to "establish" a character, but at the same time, open in his mentality to work in many situations. Again, without it seeming out of place. It's just kind of bad that DC can't seem to get Aquaman back to his roots without immediately ripping them out from under him.
And dammit, Namor was here first.
*What were they, brother and sister?