'Ubuntu is "user friendly"-ier than Windos for ONE thing setup a dev environment.'
Well, apt-get is pretty sweet in general.
More to the point, while Windows Ruby dev is certainly doable (and I did it for years with comparatively no more hassle than on Ubuntu), the advantage of developing on Ubuntu is that it is far more likely to match your server environment.
It sucks big time to be cruising along and then discover that some plug-in or tool that would solve a dozen problems for you requires a C compiler and a POSIX environment.