I was so fucking impressed with the lower powered Centrino. In terms of 'noticable' performance, its rated at 1.4ghz.. But man, I can't actually tell the difference between performance on my 3.2ghz P4 workstation.. Then, in NFS:UG its just as quick, with NO performance decrease.. Totally impressed.
They are more expensive though. But like someone said: No heat, and no excessive fan noises.
Worth the $$. Go Centrino! (Finally something innovative over 'speed').