LAPTOP Magazine Forum: P-4 vs. Centrino: "Answer:

As a general rule, the Pentium M (which, along with the Intel 855/915 core logic and an Intel Wi-Fi adapter, comprises the Centrino chipset) offers the same performance as a Pentium 4 running 1.2 GHz faster. Therefore, a 2-GHz Pentium M offers about the same performance as a 3.2-GHz Pentium 4.

At the same time, the Pentium M draws so much less electricity than the Pentium 4 that Centrino-based laptops offer battery runtimes that are up to twice as long as those of P4-based systems. Centrino-based laptops need much smaller battery packs to power them, which makes them much more compact and lightweight that P4 notebooks. Beyond that, the Pentium M also generates very little heat, which means the fans on a Centrino laptop won’t kick on very loud or very often, unlike the distracting fan noise that often comes from Pentium 4-based laptops.
Because of all these reasons, there are far more Pentium M-based laptops on the market now than there are Pentium 4-based models. Go with Pentium M."