Going from a Wii to a PS3/360 is going to be a fair graphics boost. If you like Tomb Raider, you should check out the Uncharted series. I'm sure the first one can be had very cheap (part 3 came out last year or the year before).
Playstation Plus is pretty nice. There's a bunch of things it does for you. First, at a preassigned time by you each day, it'll turn on and connect to the Internet and download and PS3 system updates or game updates. This way when you go to play, everything should be updated. Not a necessity, but nice. The main thing it does though is there are games that are free for Playstation Plus members. Not the newest games, but generally not horrible games. But right now if you're a member you can get Darksiders, Infamous 2, and Little Big Planet 2 for free (along with several others). While your membership is active, you can play the games. If your membership is inactive, you can't. If you reactivate your membership later, you can reaccess the free games you had access to before.
Certain games are free for PS Plus members for a few months. If you have PS Plus and "purchase" the free game during that time, you can keep playing those games while your PS Plus membership is active, even if you let it lapse then come back, you can play them when you come back.
They also offer pretty good discounts on other games while you have PS Plus. I think I got Journey for $3.75 instead of $15 as a PS Plus member. I was going to buy Little Big Planet 2 for $19.99 but saw I could get if free with PS Plus. Got a 3 month membership for $17.99, it came with LBP2 and a few other games to boot! Then I just renewed for a year.
need to find all the collectables and stuff now.