Username or EmailPassword
It is hard to say if Mono < or > then .NET, since it is a subset and a superset all at once.
(sortof like java = c++--++)
You could run everything that runs on Mono by installing all needed libs on .NET, but few people are going to do that and those that do will probably bee Gnome/Mono guys anyway. You can't get all of .NET running on Mono since Microsoft isn't porting and Mono isn't implementing it.
You just have two separate cultures that share a technological subset to further their own agenda.