My iPhone 4 can't do iOS8!
When I got my 4S two years ago (left my 3Gs at a bank in the hood
) I paid the extra $50 or so to get the 4S instead of the 4, seemed like a good deal for something that was almost two years newer in technology. I actually got the 4 at first then after thinking about it for a couple of days took it back to get the 4S.
IMO when it comes to tech purchases trying to save a small amount up front by buying old technology doesn't pay off in the long run.