When you put it like THAT JOE!, Pit is going to win due to his swords in close range, but Fox has technically more skill as a military trained fighter. But Pit is Captain of Heaven, so he isn't a slouch himself. The skill matchup is similar to Ganondorf Vs. Ike, but only ONE fighter has a sword.
Granted, Fox is smarter on the go, and Pit has, arguably, the better close range weaponry. So when the two can just camp all day, it really comes down to if Pit can get close enough to attack Fox.
Also to Dryn's counterpoint:
Yes, the thing is: whatever powers Fox's pistol is likely nonexistent, save for what is left in his gun. Also, the DEFINITION of a laser, or at least the closest kind to Fox's ammo, is a device that emits light (electromagnetic radiation) through a process called stimulated emission. A type of stimulation includes pumping the laser material with a source that is itself pulsed, either through electronic charging in the case of flashlamps, or another laser which is already pulsed.
Plasma, due to its unique aspect of allowing its positive and negative charges to move independently means plasma is highly electrically conductive, thereby responding strongly to electromagnetic fields. Now, recall that lasers are emitted through a stimulated emission, which is, assuming Fox's technology, to be the plasma. The type of stimulation I refer to can include a secondary source which may conduct the plasma into its containment. The plasma conducts electricity at a rapid degree, due to its strong reactions to EM fields, thus heating the laser to a high enough temperature so when it is discharged, it forms into a rod-shaped projectile that burns any object it may touch at a degree equal to the temperature of the projectile.
Now, this is assuming Fox's technology is even SOMEWHAT relevant to our world of physics and chemistry. Asking for the source on such matters is irrelevant when considering this is a battle taking place in the REAL world; not Fox's world.