Having just gone through the CentOS7 Desktop experience I would say that Mate is, for all intents and purposes, Gnome2 on CentOS-7. And KDE is, essentially the Windows XP desktop brought to Linux. Obviously there are differences, some more visible than others, but I believe that if you liked the XP desktop then go with KDE and if you preferred Gnome2 then go with Mate.

Whatever you do, ditch Gnome3. It is an exercise in futility to try and get anything useful done in the way of sysadmin from the Gnome3 desktop without having to first research, install and configure a significant number of add-ons. None of which are guaranteed to work with the next point release of Gnome.

Do not count on your current feeling changing in that event. We had multiple copies of RedHat EL for several of the early iterations and we moved to WhiteBox -> CAOS -> CentOS. Primarily this was because, in most cases, we got quicker and more accurate answers to our support related questions on forums and mailing lists.

I am sure RedHat support is of great value to many companies. Probably it is the case that the bigger the client is the better the value received. But for us the benefit obtained did not warrant the expenditure made. And, given the installed base ratio of CentOS:RHEL, I infer that this is the case for many, may others.