sweet, I was following a thread at mac-forums.com that says the 14 incher has a little bit more battery life.
I've heard the same thing a few times but I really doubt it's true, and if it is, I don't think the differences would be all that major.
I've actually gotten close to seven with mine before- but that was with all the settings turned down.
Yes, the 14" iBook has a larger battery. However, it also has a faster processor and a larger screen to light, so it uses more power than a 12". So it's a crapshoot.