According to his numbers, a real speed boost was made in compile time when PHP 5.1.6 came on the scene. PHP 5.2 changed things very slightly, slowing things down just a bit (on both the GCC 3.4.6 and 4.1.1). The ICC compiles saw a similar jump in speed with 5.1.6.

So which is faster overall? Well, as the last graph shows, even starting from PHP 4.4.4, the ICC with the "fast" option beats either version of the GCC compiler by a good margin.

Oh, and if you'd like to run some stats yourself, he includes the raw data he found when making the compiles.