I_Cheat_U_LOSE
Sucks 2 Be U
First of all Chris and Leon are allies and would not fight each other. The only way they would fight each other is if one of them betrayed each other or one of them was infected with a virus that brainwashes them.
If Chris is brainwashed then Leon will find a way to snap Chris out of it and Leon wins, vice versa.
Now if Chris or Leon betrayed each other and are now enemies:
-Chris is stronger (bolder-punch), has better endurance (can take more damage), and better with firearms (was an ex-marksman)
-Leon is more agile (seen in surviving death traps in RE4 and degeneration), resourceful (good judgment on where to jump and which ledges to hang on to), and better at martial arts (can match Krauser with a knife)
If they fought each other with guns, Leon’s agility and good judgment will cause him to dodge and evade a lot of Chris’ shots. But eventually, Leon will slip up and make one mistake and it only takes one well-aimed bullet to kill Leon. So Chris would win but without taking a few rounds in his chest from Leon before he shoots and kills Leon. He would die within minutes without medical attention from the blood lost.
If they both ran out of bullets and now had to fight hand to hand or with knives, Leon wins no contest. Chris might be stronger, but an attack is useless if it misses. Leon will have to whack Chris with a couple of hits before Chris goes down since Chris and pretty high endurance. Ultimately Leon will be winded and out of breathe after the fight, but he will defeat Chris in the end when it comes down to melee on melee.
Since RE is a game where you primarily fight using guns and its bullets that kill, Chris has the overall advantage.