While I tend to agree with eww, I will respond by saying if you go to the HP, Dell, etc. sites and read many of the threads here, just like the ones here, you will find that by far the majority of the problems are caused by router issues and interference, not by problems with any of the computers.
The problem is WiFi itself and whatever brands you look at people have problems with at as it tends not to be plug and play in far too many instances. The WiFi technology that Apple, HP, Dell, etc. are using is identical, Apple may call in Airport, Airport Extreme, etc., but it is still 802.11x and a standard.
That said I did have a problem with the wireless on a PowerBook G4 I once owned while on a road trip to Washington D.C. While in Nashville the connection strength became sporadic and was gone completely by the time I got to D.C. I went to the Apple Store in Bethesda and they spent 3 hours looking at the machine, doing an archive and install, etc. and we all came to the conclusion it was a hardware problem. I took it to the nearest Apple Store to me (Southlake, Texas), they did a hardware test on the DVD drive and it was faulty. Why the DVD? A shared circuity with the Airport card. They replaced the DVD and I never had any more problems with WiFi and the person I sold it to has had no problems. I've had not WiFi problems at all with my 15" MacBook Pro (February 2008), none with a PowerMac I owned and none with my Mac Pro.
Seems like you did some research before you posted your question, which is a bit disingenuous. Are you a troll?