Text isn't as sharp on the 14" ibook as it is on the 15" AlBook. Also, everything that displays on your 12" G3 iBook will show up exactly the same on a 14" iBook, so you don't get any more screen real estate--everything simply appears larger, including text, which may be more comfortable depending on your eyesight.
You should find a store where you can compare display models. Be sure to open the same 'read me' document on each model to compare the text sharpness. When I was reading a lot of text on a 14" iBook, I got eye fatigue. YMMV.
PS: text appears sharper on the 12" iBook.