12" ibook G4, 1,33GHz, mid 2005 (it has the shock sensor, too).
better graphics card, than 12" powerbook. The ibook has a ATI 9550, which is a crippled 9600, it even displays *mts2 files under 10.5 and VLC. The 12" 1,2GHz ibook had a 9200 and that can't handle these files (only like 5 frames out of 10minutes, stop motion show). The 12" Powerbook had the Nvidia 5200, which was to be said, inferior in power, to the 9550. I didn't have this myself, though.
But, with the 12" PowerBook, you have 1,5GHz versus 1,33GHz (a difference of 0,1GHz between the ibook 1,2GHz and 1,33GHz, for me resulted in 30min. shorter encoding time for a 23min sample. The whole time was 12h30m, if I remember correctly (with h.264).
If one goes for the 14" ibook G4, he has 1,42GHz, so maybe, if encoding gets shorter by 30min, for 0,1GHz, than it might be an 45-60min, here. Of course, the 12" PowerBook, would then have 1,5GHz.
But, when someone takes the 14" ibook, he can even take the 15" PowerBook with 1,67GHz and ATI 9700.
If it is not for the looks, white versus aluminium.
The shape difference is:
PB G4 15"
1.1 x 13.7 x 9.5
Avg. Weight: 5.6 lbs (2.5 kg)
Details: In inches while closed - height by width by depth, (2.8 cm, 34.8 cm, 24.1 cm).
PB G4 14"
1.35 x 12.7 x 10.2
Avg. Weight: 5.9 lbs (2.7 kg)
Details: In inches while closed - height by width by depth, (3.4 cm, 32.3 cm, 25.9 cm).