From my own experience: try a few, and see which one you like. I tend to switch once in a while, for instance when Ubuntu went nuts with their Unity interface. Totally designed for Newbies, but I didn't like it.
I've also switched between Gnome and KDE a few times. They all tend to get more demanding and animating. Try Knoppix (boot from DVD without installation) to see how crazy animations can get: the last one I downloaded had "magic lamp minimize" and "wobbly windows" by default.
After this, I'm down to Linux Mint now. With adjusted Appearance: I want my active window to have a clear blue border. The default is dark and barely shows which window is active. Clearlooks is a good start for Appearance, but I've customized it further.
Good luck
It's all about taste