If Squall gets a shot off then he'd kill someone. Other than that his tight hipster leather pants and assortment of belts are far too inconvenient to be flexible and nimble in combat.

By that same token Tidus has the most flexible clothing but also has a lot of bare flesh so would be very susceptible to getting hit.

Cloud is the most appropriately attired but has a gigantic sword which probably takes an age to swing leaving someone more flexible like Tidus to get a hit in.

In short, none of them. Irvine would shoot them all and then whip his hair back and look fabulous whilst strutting off into the sunset.