Captain Britain the once alcoholic, very emotionally unstable Captain Britain (Brian Braddock)? I'd give this to Captain America. Bucky's death didn't cause a complete mental collapse and although Captain Britain is stronger and faster, Captain America has faced far tougher opponents.
If another Captain Britain, I'm unfamiliar with them.
There are two threads with these two characters if you have searched.
http://www.killermovies.com/forums/showthread.php?s=&threadid=310868&highlight=captain+britain
http://www.killermovies.com/forums/showthread.php?s=&threadid=290552&highlight=captain+britain
Marvel Directory's stats are out of date. Here is a more recent stat of Captain Britain:
Captain Britain originally wore the mystic talisman known as the Amulet of Right, which could replenish his superhuman energies. Captain Britain also wielded a star-sceptre, a mystic weapon that he could utilize in combat as a quarterstaff. The sceptre also allowed him to fly, and could generate a protective force field about his body. These two objects were later remade by Merlin into a lattice of mystical "micro-circuitry", a costume that duplicated all the properties of the original artifacts. Captain Britain subsequently believed that his superhuman powers were dependent on the costume, which he thought amplified his natural physical abilities and projected a mystical force field. However, he has since learned that he himself possesses these powers due to his being of Otherworldly descent. The costume served to help Captain Britain make use of his innate superhuman abilities while they were still in the process of emerging from latency, a process that apparently took years.Captain Britain possesses superhuman strength that allows him to lift approximately 90 tons under optimal conditions. He also possesses superhuman stamina, reflexes, and can fly at a maximum speed of just under the speed of sound (770 miles per hour) for prolonged periods of time until bodily fatigues require him to rest. The mystical energy within Captain Britain's body also makes him highly resistant to physical injury. He can resist even a bazooka shell without rendering him unconscious from the concussion. Repeated blasts would weaken the field considerably, and eventually penetrate it. Captain Britain is also immune to the adverse atmospheric effects of flight at high speeds.
Captain Britain's superhuman powers and life force are mystically dependent on the lands of Britain. If he travels away from Britain, he will grow increasingly weak the longer he is away. Staying away for an extended period of time runs Captain Britain the risk of death.
Captain Britain currently wields Excalibur, the Sword of Might, forged in the fires of creation and tempered by the power of the universe. United with the Amulet of Right, Excalibur possesses the capacity to remake the cosmos. Both talismans of power formerly belonged to the god-wizard Merlin.
Cap is the man, but eventually he will lose to Captain Britain.
Captain America wins! Why? Because he is Captain AMERICA! Americans will always beat the Brits. Americans drink COFFEE,Brits drink TEA.....Brits have a social medical plan which leaves most Brits with bad teeth...Americans have a better dental plan or the cash to get better dental work....Better teeth combined with coffee gives Captain America the victory!