I would say the 14" iBook, since you seem to want a 14" screen. The 12" is fine, but if you want the larger screen, the iBook is a good way to go.
However, you did say that you wanted to do gaming. I would highly suggest waiting for iBook vs 12" PB gaming performance.
Also, if you are are serious about gaming, I would very highly suggest a 15" PowerBook. It has the Radeon 9600 Mobile with 64MB DDR RAM. This is out preform the iBook and 12" Powerbook by at least 2 times.
The 15" Powerbook, IMO, gives you a better value for the money. I bought a 21" Trinitron monitor with my Powerbook and find myself using the built in screen 9 out of 10 times while sitting at my desk. The screen is very sharp and the resolution is good enough for almost any task.