Whichever is best for you. I'm just a little biased towards 3rd because that's all I know.
You can still buy 2nd ed. stuff, they are just harder to find since they are not in production anymore.
One good thing, if you've played BG/BG2 and ID2 you can probably compare, is that 3rd doesn't have race-class restrictions. Either way, I hope you enjoy the gaming experience
