For the Street Fighter Collection, the PlayStation ports of the Super Street Fighter II games are some of the best out there, and are apparently better than the Saturn versions, which have slowdown and I think slightly stretched sprites or something along those lines. There was discussion about it here like a year or two ago.
From what I read here and on other sites, it's basically Dreamcast > PlayStation > Saturn.
It's a bit hard to believe, because the Saturn is made for 2D, but it seems like the messed up a little bit on the Saturn version. It's still pretty good, though, but the PlayStation version is better.
I own the PlayStation version, and it's great. I play it on a PlayStation 2 with fast loading on, on a CRT with component cables and a MAS arcade stick, and it feels pretty much like playing the arcade version. I originally wanted to get the Saturn version when I bought it (sometime in the late '90s), but I guess it's good that I ended up with the PlayStation version instead.
Street Fighter Collection also comes with Street Fighter Alpha 2 Gold, but I never looked up how the two versions compare. I only played the PlayStation version a bit, since I have regular Alpha 2 on Saturn, but it seemed pretty good from what I can remember.
Stuff like X-Men vs. Street Fighter and its follow ups are missing a lot of stuff on PlayStation. No tag! Always go with the Saturn and Dreamcast versions of those.