"The 750 is a bit faster, but it is 25% more expensive for less than 25% more performance."
Please show relevant benchmarks. I've done a lot of research on this, and i5 750 is a lot faster in pretty much everything else than gaming, where they are more or less equal (GPU performance is more important there).
"The latest generation of AMD chips also has adaptive clock speeds to improve performance on monolithic tasks, soon that will be available on the x4 chips as well as the x6."
And Intel's new chips use very aggressive load balancing with the new quads: For example, on a basically single-threaded load on one core the core is actually overclocked to get more speed. Both manufacturers have good tech in place, ATM Intel's seems better to me, according to benchies.
Don't get me wrong, I don't advocate buying Intel just by the brand, either. It's all about the uses and budget; my budget at the moment would mean an AMD Athlon II X3 with nVidia GTX 460 1 Gb, as my main uses are gaming and programming. If I could raise my budget a notch, it'd be i5 760 with the same graphics card. Of course, I'm from Europe, so the price difference between i5 quads and Phenom II X4s is a lot less than let's say Newegg's prices in the USA.