You could also compare the EVGA 9800GTX ($330) vs the EVGA 8800GTX ($340 before rebate, $290 after rebate) and honestly even if I wasn't going to cash the rebate for whatever reason I'd still pick the 8800GTX.
From what I understand OC'ing the G92 does not net you the same performance benefits as OC'ing the G80 core (At least that's what I'm led to believe by some of the comments of G92 owners in this forum). The other thing that worries me a little about OC'ing these cards (That may or may not be fixed with the 9800GTX) is the fact that there were some strange problem going with the memory I believe when it was OC'ed past 2000 that affected the longevity of the card.
For what is worth, the 9800GTX is no doubt a great card (No matter how you look at it, it's a rehashed 8800GTS G92), however the 8800GTX still feels like the better "high end" package to me if you get what I mean. One thing that cannot be denied is that you will need a PSU for the G80 core to feast on, because they are power hungry.