Like it was already stated it depends on what your needs are. Personally I'd stay far away from the 2xxx versions as I've personally seen issues with them and I've seen threads about them as well (In my particualr hardware configuration I can not reboot any of the 2xxx versions properly).
Use 3xxx versions if you use Win8, if not you can also use 1xxx versions. If overclockability is your requirement you'd have to test versions yourself with your particular hardware combination. If stability is your main concern, the latest versions incorporate more fixes.
Unfortunately there's not a catchall answer for this question.