Core I7 vs. Core I5

Really two reasons:
1) The LGA 1366 has only a marginal performance increase for gaming, so the increase in performance doesn't support the cost increase when the end user won't notice the difference.

2) x8,x8 performance in SLI/Crossfire still performs well in gaming. The end user will not see the difference in performance between x16,x16 & x8,x8. By the time x8,x8 runs into a bandwidth issue, newer technology will be out that warranties further updates overall!!

In the end, it your decision to make. You can't go wrong with either decision. I support the LGA 1366 system myself over the LGA 1156  

The i5 is significantly cheaper so it will reduce the total cost of the build or allow more to be spent on the graphics card. Also in games the i7's perform slightly better than the i5 which performs slightly better than the PII 965 so the gaming difference isnt too much between them. Also having only 16 lanes wont really hurt crossfire or SLI, tom's tested and it showed that there was only a marginal difference between 8x/8x CF and 16x/16x CF with 5850s so it doesnt really affect upgradability.

You must realized, though, that the LGA 1156 platform will MOST LIKELY not positively not receive any upgrades to it's CPU choice in the future. So the end cost of buying a i5 vs. lga 1366 i7 would turn out more for the i5, because you would have to buy a whole new platform to get any more performance out of the cpu area.

That sounds a little confusing the way you wrote it, but if what I understand hold true:
Socket 1156 would be a better choice for upgrades because Intel's next microchip design is going to fit into the 1156 socket. Whereas the 1366 socket was a stepping stone to the 1156 socket, and will have no further chip designs that fit into it.

On a side note: the turbo boost on 1366 only goes to bin 2 (266mhz), but the turbo boost on 1156 goes to bin 5 (677mhz)

Hope that helps any confusion.

The next Intel chip (Hex Core) will be on the LGA 1366 socket... not the LGA 1156 socket. You had it backwards in your response.