Ah ha ha! I've been waiting for this one!

Luigi wins. No contest. Why? Because he is an absolute badass. In addition to Luigi's SSBM abilities, he has a set of skills from one particular game that make him nearly untouchable.

Mario and Luigi: Superstar Saga. A Mario RPG on the Gameboy Advance released last Christmas. You play as a party consisting only of Mario and Luigi. No other playable characters. Now, the interesting thing about this game is that it plays very differently from a normal RPG. Yeah, you guy new armor and accessories. Yes, Mario and Luigi recieve new upgrades to their weapons. Yeah, it utilizes a turn-based combat system. However, the combat in the game is a lot more involved than a normal RPG. You can't afford to just try and shrug off attacks like in a Final Fantasy game. In order to deal with damage from the enemies, Mario and Luigi have basically two options at their disposal. One, they can dodge the attack altogether, or two, they can reflect the attack back at the enemy with their hammers.

Mario and Luigi are capable of nullifying, avoiding, reflecting and counterattacking every single enemy attack in the game. There is not a single unavoidable attack in the game. That right there speaks volumes about Luigi's maneuverability. The fact is, if an entire legion of nasty enemies can't hit the guy, what makes Fox any different? If the final boss is incapable of hitting him, what gives Fox the advantage?

On top of that, Luigi's hammer can be used to reflect any and all energy-based attacks right back at the enemy. That right there completely nullifies Fox's blaster and his reflector abilities.

On top of that, Luigi has an assload of experience going for him. He's much more suited to face-to-face combat than Fox is. Fox has been featured in a total of three games in which he's had to take enemies on face-to-face. Luigi has been featured in at least ten. So, experience in hand-to-hand combat is also more in favor of Luigi.

All in all, I have to give it to the L man. He's mean, he's green and he'll remove Fox's spleen...if so inclined.