Which two are you currently looking at? Realize that hyper threading creates logical cores, which do not process as many instructions per clock as a physical one would. If you are looking at an i3 vs an i5 the i5 will will in multithreaded tasks, but most games are still only dual threaded. You have to consider more than just the CPU, what will you be using the system for? Whats the budget range? Is the hyper threaded dual core significantly cheaper than the quad or are they fairly close? If they are fairly close go for the native quad.
If that seems a little costly then the i5-750 ($200) will still be enough for any GPU setup out there so far and into the future, the i7-920 on LGA 1366 will just give you a bit better future-ability and upgrade path.
AMD is still a great choice and is strong enough to power most GPU setups out there as well (if using the Phenom II 955 or better). However if you can afford it the intel is worth the price premium and will last you a bit longer without bottlenecking future graphics card setups.
Either way you go you'll be more than impressed. HF.