Sorry, I disagree, the benchmarks I've seen show centrinos outperforming G4s.
( ONE example benchmark comparison:
http://barefeats.com/al15b.html
)
yes, I know benchmarks are hit and miss, but a guide. Also this benchmark does not show 1.67Mhz G4s ( the fastest G4s that Apple use ) but really, these aren't going to out perform those Centrinos in the benchmarks)
The 7448 PPC is a mute fact... Apple don't use them, they may well be faster, however, they aren't being used.. they may well never be used.
Todays G4s that are inside Apples are crippled due to the limited bus speed where as the centrinos don't have this problem. They can use DR266 memory to their full potential. Bus speed alone makes a difference.
Apple battery life hasn't increased significantly in recent times. The battery life in Centrinos are better, and getting better, whilst G4 battery life are quite static. My powerbook battery won't last more than 2 hours in PRACTICE ( not specification ), which is pretty poor these days - and its less than 6 months old.