Are you sure this is accurate? HT is a CPU Level implementation which enables your CPU to effectively double its number of cores. To test this, encode a video and you will see 8 cores using 100% of a CPU rather than 4 (tested on a i7 Win 7 machine). Grand Central Dispatch is a S/W level version of this (which leads me to think it wont be nearly so effective).
In all PC benchmarks a i7 860 performs video encoding much faster than a i5 750. I assume it will be the same for a Mac.
yes, HT is only virtual, so the other 4 are just 4 virtual cores, like someone said here, or was it the other thread, nothing beats the real thing.
Basically its like this, in order to take advantage of multicores, multi-threaded apps are made.
Chrome is actually a good implementation of multi threaded apps, what they did is actually make a new process of the browser, so that each windows has its own process, giving the OS better management overall.
In the link you provided, indeed handbrake gave 37% speed gain, but note that iMac uses the i7 860, that 37percent is for the i7 870. Anyway, its roughly 26% ++. The point here, is that handbrake is designed for HT technology, that's why you are seeing the speed increase. So if your app isn't designed for HT, then it doesn't see the same increase, so its like a 100Mhz speed bump.
Moreover, like I said, Grand Central Dispatch is Apple's own solution for making apps multi threaded, basically all apps, will be multi-core aware. So its like the software implementation of HT only better, because its built in right into the OS.
So basically all apps that uses GCD Api's will make that app multi-core aware. Making the i5 and i7 almost equal, since its like squeezing every drop of what i5 chip.
In my humble opinion, I don't like HT at all, in some instances, its even slower than with HT off. HT was actually part of pentium 4 which is actually a failure (worst chip intel ever made), but it was removed when the multi cores are invented, now Intel brought back HT I don't know why
