Get OP, absolutely, it's cheaper. I'll also direct you to the following thread:
http://www.dynaverse.net/forum/index.php/topic,163353401.0.html To me OP is where it is at, it's a deeper gaming experience on many levels. SFC3 is also much more expensive, I believe. If you've got the excess cash lying around then I suppose you could go for 3 as well. I feel I must say this, however, every one of my friends that plays SFC was horribly disappointed with SFC3 (even those that don't, or haven't ever played SFB) and many returned the game or traded it in and were very angry for having to have done so. I'm not saying some don't enjoy it, but I didn't warn my friends because I questioned my own judgement on it and figured I'd let them make up their own minds (this was mostly due to a great many debates and I figured I'd keep an open mind and see what others thought of it), and they were pretty ticked off that I didn't shy them away from spending the cash on the game, so now I'll do so. SFC3 does have some nice features that a lot of folks wanted, but it stripped far too much out of the gameplay and immersion, without putting in adequate replacement.