If we're talking about mass adoption of Linux then there really has to be no concept of even "picking a camp". The vast majority of users - even techy people - will not understand what a window manager is, never mind be capable of choosing one.
Yes, there are many UI implementations in Windows but they are almost totally transparent to the user (no pun intended), and they can all run on the same system at once.
Yes, there are many UI implementations in Windows but they are almost totally transparent to the user (no pun intended), and they can all run on the same system at once.