I have some side-by-side experience with both MacBooks (black and white, though there isn't any difference in their wireless systems) and my own MBP. We seem to get about the same quality of signal most of the time, even in poor coverage areas. I was rather surprised by this, but I've confirmed it with other people's MBPs; Apple seems to have actually managed to get past that "metal cased laptop antenna problem" from the TiBook days. Also, keep in mind that the actual hardware in MBs and MBPs is much newer than what's in iBooks and PowerBooks, and that makes a difference in how well signals are handled.