I haven't played the PSN version of X-Men Arcade, but I've heard the netcode is really ty so playing online sucks. Offline multiplayer was great in the arcade version and I'd imagine that's unchanged. If you're asking about the specifics, it's a basic arcade beat-em-up like Final Fight.

Warrior Within isn't worth playing for free. If you want to play a Sands of Time game, I say get the first one or wait for The Two Thrones.