Basically...although there are a lot of variable to take into consideration here ie. drive quality, firmware and media quality as well as compatibility with all the above. Typically your burner will be the static variable with the media being dynamic, but you also have other things going on with your PC that can influence burn quality such as virus scanners, background operations etc.
Back in the day it was suggested to burn as slow as possible for better quality burns, this logic can be reversed now. Sometimes faster is better because media and firmware are designed for higher speeds....which also means slower is worse.
Beauty is in the eye of the beholder.....
Lots of media has been tested for you here ~ http://forum.imgburn.com/index.php?showtopic=2833