Was the MacBook one of the newer ones with the aluminum unibody frame? (Probably not if it only had 10.4) apparently they feel more solid now. I could tell the difference between my old 17" MBP and a newer unibody 17" MBP.
As another poster mentioned though, the white MacBook is a replacement for the iBook and built to a lower quality therefore.
A far cry from the flimsy sheet metal feeling of the PowerBooks and MacBook Pros of old.