Even out of armor and at a young age, John was an impressive hand-to-hand combatant as well as strategist. He was actually challenged by a few grown-ups in the first book, and he took them down quite easily. He is also enhanced, meaning his strength, speed, reaction, etc., have been increased to near-superhuman (in the armor he'd be superhuman class). I'm giving my vote to Master Chief, considering his physique would be particularly greater now than it was as a child.
@HereComesTheBoom_Headshot: I beileve he is superhuman outside of his armor as well. If you want to use marvel/dc as a standard... MC can life 3x his own body weight, and considering he wieghs almost 400 pounds that is a lot. He probably around 25-30% stronger than a peak human of marvel/dc comics.
Then again i dont know too much about conans physical abilities
@HereComesTheBoom_Headshot: Initially I was of the same mind...i mean, John is a meta-human much like Captain America; however, I also believe that, much like Batman, Conan's life of constant war made him to be something comparable to John. Why I give Conan the edge is due to the idea that his entire life consists of one brutal mele to the next. Now, get get me wrong, I know John is not a slouch when it comes to throwing fisticuffs, but his career in war is primarily as a trigger-man with amazing tech armor (over-simplified I know), whereas, Conan never wears armor, and tanks all of the damage he receives with his body, which IMO gave hima tolerance to pain that can withstand a lot of punishment, even from someone as strong, fast and agile as John.