What exactly are you looking for? They are same card, thus the same speed. Many times the iBook has slightly better reception/range than the PowerBook. Its not too much of a difference though. This is due to the case and antenna, not the card.
The simple answer is 'the PB's AP is fine'. It's at least on par with other wireless cards, but I think it is probably better.
The complex answer is 'who knows?' It depends on the size of the room, construction of the walls, interference from other devices (wireless phones, microwaves, etc).
If you're asking if it's worth getting an iBook over a PB for reception, I would say it's not a big enough difference to make a deal. They both KILL pc laptop's with built-in wireless.
My 15" PB has fine wifi reception.
At home, I'm one floor up through standard building materials, about 20 feet in a straight line from the AExpress. Printing via Bonjour is a snap, too.
At work, I am perhaps 50-60 feet away, though one cinderblock wall and several sheetrock walls.
I have no problems with reception on my powerbook, i don't live in a very big house, but it works fine in any room, and outside too
Also, i've set it up on the back seat of my car while driving, running KisMAC (wi-fi detector software) and have it find networks on fairly wide roads, even in fairly busy enviroments
Note: Powerbook is on back seat with the screen off just recording all detected networks, without any interaction with me