Well instead of these theoretical answers, I'll give you a real answer.
It depends on how much money you have. While it is true that LGA 1156 only supports x8/x8 crossfire/SLI, that won't bottleneck any single GPU card noticeably, some articles cite +/- 4% bottlenecking which is well within the realm of variability meaning it could be even more irrelevant. That said, if you ever plan on having 2 dual GPU cards, like the GTX 295 SLI or 5970 crossfire, then the x8/x8 will be a bit of a bottleneck.
As for the platforms themselves, LGA 1366 gives no noticeable or tangible benefit in gaming or non-gaming apps over an LGA 1156 quadcore with hyperthreading (i7 860 or Xeon X3440). The triple channel RAM is really the only other thing that differentiates the two platforms, and triple channel RAM does not show improvement in almost all scenarios. The i5 750, without hyperthreading, will give you plenty of performance and will come very close to the performance of an i7. As for hyperthreading itself, it really only helps when you have multiple multi-threaded CPU intensive apps running at once, such as WinRAR, HD encoding, media converting, and media editing.
Another option, should you think about getting 3+ cards, is an AMD system. A Phenom II X4 based system will be cheaper than either the LGA 1156 or the LGA 1366 and will provide the exact same performance in gaming and has plenty of motherboards that allow for x16/x16 crossfire or more. That said, in a few non-gaming apps the Phenom II X4 system will not perform up to par with the LGA 1156 and LGA 1366, but for many that is irrelevant.
It all depends on what you can afford and what you want to do. If you are a pure gamer, with maybe some light HD encoding on the side, then either the LGA 1156 or AM3 platforms will give you all the performance you need. If you plan to use 3+ GPU (ex. 3 5850s in Tri-crossfire or 2 5970s in quad-crossfire) then the AMD system will give you all the performance of the LGA 1366 for less.
A side note about the LGA 1156 system, is that you should avoid the dual cores (i3/i5 6xx series and Pentium G6950) as they can not match the performance of a actual quadcore and are not priced well. The ~$100 i3/G6950 is bested by the Athlon II X4 620 @ 3.2+ GHz because it is a quadcore. Anything above that remains in direct competition to even faster quadcores, which makes the more expensive LGA 1156 dualcores even less appealing.
Finally you must consider the features offered by these platforms. While the AMD system will provide the same performance for less money, the LGA 1156/1366 provide a few benefits. Most P55 and X58 boards can support SLI AND Crossfire on the exact same board, giving you more options in the future. This is a bit irrelevant if you do not have very quick upgrading habits.
Also, it is possible, though their are rumors against both of these points, that the LGA 1366 and the AM3 chipsets will get the first hexacores or 6-core processors. With Intel, expect hexacore prices to be ~$1000 or more while the AMD hexacores will be far cheaper. The problem with this is that it is rumored that not all LGA 1366 boards will support these new CPUs and that AMD might use a different socket for their hexacore CPUs.
It all comes down to price, in my opinion the Phenom II X4 925 @ ~$120 is the best price v. performance CPU on the market for gaming, but there are so many variable that the right product for that fits your needs could be vastly different.