Celeron is NOT better than a P4 notebook. however, Centrino is better than P4 for notebooks.
for notebooks, look for a Pentium M Processor, not a P4. P4 was really designed for desktops, so won't get power savings like you would from a Pentium M.
Centrino is just a marketing term used by intel. to be labeled as Centrino, it must consist of 3 components. 1) Pentium M processor 2) Intel 855 chipset 3) Intel PRO/Wireless 2100 (IEEE 802.11b) or PRO/Wireless 2200 (IEEE 802.11bg).
Pentium-M 1.7 would be comparable to a P4 3.06.
For mobile computing, Centrino is the way to go. hope this helps.