FPC and La Junta are not better then one another they just require a different playstyle.
It used to be FPC was a power clan and La Junta was a Ability clan. But with the powercreep almost all cards have abilities so it has shifted to a versatile clan FPC, and a mono clan La Junta, neither is superiour to the other. As the true strenghts of La Junta come out in Mono while FPC has some of the greatest half decks around. FPC has always been getting the crappy cards though, but they're on the rise now and certainly can beat La Junta pill for pill (unless you count in General Cr)
But mostly some people are better with La Junta, others with FPC it depends on how you play your game.