Also, if you do anything such as video editing and encoding or 3D rendering then ensure you go for either an LGA1156 or LGA1366 Core i7, not Core i5. Which platform depends on other factors though, such as those Maziar listed.
Erm with regards to 3D rendering the LGA1156 with a Core i7 860 vs a Core i7 920 on an LGA1366 show the 860 as being just as quick if not quite a bit faster then the 920 according the review that Maziar posted. The same goes for video encoding with the 860 performing just as quickly as the 920 if not faster just by a whisker. I'm comparing the 860 and 920 since they are similarly priced where I live (UK).
Gaming performance is harder to judge since it's the video card that does most of the work these days but you still need a good CPU to avoid bottlenecks, the 860 has a default clockrate of 2.8Ghz which is slightly higher then the 920's 2.66ghz however that's not where the advantage is for the LGA1156 chip. The new Core i7's have a very aggressive Turbo mode which automatically overclocks the CPU when it's pushed, the 920 has a Turbo mode as well but it's no where near as fast as the new chips.
The argument of being limited to x8/x8 when running crossfire on the new Lynnfield chipsets is a none argument as well, just reads Tom's review on the Radeon HD5850 running on x8/x8 which shows there is no bandwidth limitations. Taking this a step further over at TechPowerup they found even if you go down to x4 the performance drop isn't that great.
The best arguement you can make for getting a LGA1366 setup over a LGA1156 is that you will have a board they 'may' run Intel's up and coming Gulftown 6 core CPU's. If this is plus for you I should let you know that any 6 core monster is going to cost $1000 minimum and I wouldn't expect to become affordable for at least 18 months or two years afterwards.
I never said that LGA1366 is better for 3D rendering. If you read what I wrote, I said go for either LGA1366 or LGA1156 Core i7 (which includes both the 920 and the 860), just not the i5 (which is just the 750 at the moment). Although the i5 750 would be fine for occasional rendering, just not if it's your primary use.
Thanks to all for your respond.
I had read some reviews and I saw that the Core i7 860 and the Core i7 920 have almost same numbers on the tests. But that do not help me a lot to make decision. At most I’m worry about the future. I’m tired every two years or so to replace whole system when I do upgrade. Is there any news from Intel about the future? Are they will continue to make LGA 1366 and LGA 1156 or they will discontinue the unpopular one? I’d like my next upgrade to be just for the CPU.
As for future proof (if there is such a thing ), you will be alright with either. Some say that the 1366 will be more "future-proof" because you will have a 6-core option. I'd say for $1000, I'd rather build a whole new system. Especially when new features (ie USB 3.0) start coming out, you'll want a whole new system anyway!
JeanLuc - you took the exact words out of my mouth.....