IMO, The real reason "most" developers switched to mac has more to do with hosting websites on Linux/UNIX than anything else. A true UNIX command prompt is a powerful tool for dealing with large numbers of other UNIX computers and computer files.

SSH + vi and suddenly your not just using your system but any computer your connecting to. The classic windows advantage of all those legacy systems stopped being relevant when many developers went back to notepad to update whatever new language they happened to be using today.

PS: The article mentioned Terminal, but it forgot a lot of the other out of the box UNIX tools like SSH / diff.