Go for the Refurb. The processors in the high end iMac are the same as eth last generation, just with a slight speed bump.
Unless you plan to spend a lot more and go with the SSD, you are better off with the refurb i7.
The refurb is so much cheaper if you are looking at i7 and i7. Heck, even the new quad i5 is more expensive than the refurb i7
I returned the new i5, paid the restocking fee, bought the refurb i7 overnight shipping will be here in a few hours and still cheaper.