Just speculation here, but I suspect the time to compile has little to do with the complier, but rather the way Visual Studio is architeched. There are layers-on-layers of half-assed fuctionality build on top of everything in VS.

While you might want to just compile a release version your program, Microsoft has other priorities. Initialize profilers, networking subsystems, debugging support, check the internet for whatever-the-fuck, check drivespace on drives you're not using, see if bill gates' dead grandma's cookies have been delivered...