uh, slant six wasn't a big psp developer at all. they were the dev who handled socom when zipper said "let's make MAG" but before zipper said "wait no one care about MAG back to socom." originally zipper made the PSP socom games, and then slant six took over and also worked on the first PS3 multiplayer only one.
slant six is in the same area as rebellion. like a c-tier developer publishers go to and say "we need a new alien vs predator game, quickly, and we don't want to spend a lot of money"