YOU GUYS REALY THINK THAT??? In my opinion I'd say the spartan would win he has the augmentations, armor (even without shields and comp it works because of recharging battery), better guns, stealth (read the fall of reach), and the plasma grenade can kill in 1 stick. so personally I'd pic the spartan.
p.s. and even 1 spartan v.s. 200,000,000,000,000 commandos would still win (read pro log in the fall of reach, and the first strike)