To answer your question,
I'd get the iBook 14 and maximum RAM.
---
I have my iMac DV SE right next to my iBook and I use both daily. I use Teleport to control the iMac from my iBook and vice versa. Works great.
I have long abandoned Mac OS 9 and Classic, so both are running the latest Panther.
The iMac merely lacks the Quartz Extreme effects, but no loss.
I bought a 1 GB ram kit for the iMac and self-installed a 7200 RPM drive in it. The little guy is a beast now. You'd be surprised just how much of a Mac's perceived speed is tied to both RAM and hard disk speed. Yes, MHz is important but not if your drive is slow and you have limited RAM.
I am a professional (web/Flash) and the combined workload done through these 2 Macs to date is roughly $200,000 (albeit not to me, but rather for companies I've worked at) and counting. No, I don't do 3D, gaming or Video, nor am I suggesting I could on this Mac.
I have never used a G4 let alone a G5.
I am Apple's best example and yet it's worst nightmare
Bottomline, try to revamp it if you get a kick out of maximizing ROI.