Depends on whether if you're going to use your notebook more for music or other things. Most people who use notebooks for music go for Pentium. Weight is also usually not a problem since we would rather trade portability for performance. If you're using it mainly for softsynths, a fast CPU with lots of RAM is what you need - and Pentium is definitely the choice. If you're thinking of recording, Centrino should be OK but you'll need a fast HD. There are notebook harddisks running at 7200rpm, but the general rule is getting an external drive. Even for desktops, we usually use 2 HD - one for applications/ storage and one dedicated for recording - otherwise performance will drop since Windows will access the HD constantly (page filing etc). Firewire drive is better than USB, even though USB 2.0 us "supposedly" faster than firewire 400. Also take note that if you're recording but using lots of plug-ins (effects etc), you'll still need a fast CPU.
