for laptops, efficiency is more important.
the G4s (in PBs) is more efficient than current G5 chips. less pipeline stages at lower clock speeds is about as good as many pipeline stages at higher clock speeds (keyword: about). this isnt all thats important in processors, but its a big determinant of "raw" speed. but as shaun mentioned, the battery life would be sacrificed to the energy gods in exchange for higher clock speeds (bigger processors, heat syncs, etc).
youll notice more improvement in system performance by getting more memory (RAM). a G4 PB with 2GB of memory would still fly. if price is what bothers you, look into buying a used 1GHz PB instead of a 1.25GHz, and the couple hundred you save can go towards the memory.
and dont buy memory from the stores unless they have some sort of free deal when you buy a comp from them. and definitely dont buy from the Apple store or apple online. they charged almost double what the store i worked at charged, and we were over priced. browse
PriceWatch.com and buy from someone with a 60% or greater feedback (this isnt very necessary since to be accepted on price watch they need proof of a few thousand sales and at least a year of business, but it means people are really satisfied with how fast they ship). i reccomend micron memory because all their memory has a lifetime garauntee, but they all do the same thing, just some have a higher yield of tested memory.
