Snake seems like the more realistic figure of a 'hero', which is why I would choose him. He has all the techniques of CQC, and overall, 'soldier' quality. In an actual fight it seems like Master Chief would win. He has a big ass suit on, and I don't see how Snake can get through it. Unless he has some kind of armor penatrating ammo, nothing will be go throughing that suit. Today's weaponry isn't as strong as they are during the era Master Chief is living. Master Chief saves the world from aliens, and other sci-fi creatures. Snake saves the world from actual people with 'super-natural' powers. We don't know how much experience Chief has on the field. Snake has a good 15-20 years? I also like Snake cause he takes the quiet way out. In Halo you don't usually have sneaky missions. You mostly run in there gunning for your life.
Snake, IMO. Just for experience, and overall pwnage.