For GNOME I picked Fedora because it offers a vanilla GNOME experience and is frequently updated while remaining rock-solid.
Pantheon, the elementary desktop, is only shipped by the guys over at elementary, so that choice was quickly made.
Linux Mint ships a great Cinnamon desktop. It has a Windows-y look, so it is very easy to learn for new users. It's also built on Ubuntu LTS, so stability isn't a problem.
For Plasma I picked KDE Neon. It is straight from the KDE developers without customization. It features the newest KDE packages while being built on a stable Debian base.
I would, however, not recommend KDE to beginners. Plasma is prone to break for people who don't know what they are doing. If you're going for the Windows look, consider Cinnamon.