Get the i5. I only got an i7 because I do lots of multi-threaded post-processing and rendering on my rig.
Good thing I came by this thread, everything apart from the bashing was quite informative. I'm going to get an i7 920 later on next month so hopefully it should be a better choice.
if they're both the same price, the i7. I'm one to cut on costs though, Cheapest i5 you can get is the choice I'd make.