If I was to choose a processor for my notebook, and I have these two choices the I would choose Centrino. Why? Because it is IMO better designed for notebooks than a Pentium 4m. You get better battery life with Centrino, and the speed outperforms the Pentium 4m even if the clock speed is lower. But of course it is more expensive than the Pentium4m, but definetely better for a notebook. IMO of course.
dan