I install PCs for a major manufacturer of PCs - that will remain nameless -- but suffice to say that I can always tell that a notebook/laptop has a Celeron inside 'cause it has a tendency to st...st..stu..stutt...stutter a little as it chugs along - I'd stay away from Cs if I were you - if only 'cause once you got it it ain't exactly easy to slip in another board or different CPU to speed things up.
P4 for me thanks.
Cheers