I bought the advanced suit and I'm using it over my DLC suit now. I didn't want to spend the money, but it was well worth it.
As far as guns- i'm maining the Line Gun now. Once it's maxed out you get extra width, electrical damage (or at least it looks like it) and speed. Also, the alt-fire is a beast. I killed 6 guys in one go at the beginning of chapter 13 with a little help from a stasis canister.
Other than that, i keep the force gun equipped for crowd control. I use it to push guys back when i run out of ammo, then once I've found some (if i haven't force killed them) I back into a corner, reload and start the real fight.
My 4th is the rivet gun, which i don't like, but it stacks well in the inventory(30 shots a stack) and it's a 1 shot kill for the smaller bad guys (it pins the little kids to the wall like the bigger gun, and it makes me laugh).
I wonder if you could do some advanced strategies with the rivet gun like the rivet mines in Bioshock.. I think the alt fire for the gun is disabled after you change clips, but I may be wrong. I'll play around with that tonight.