Visited last week.
Definitely more Europeans, including some Romanians and Turks that surprisingly weren't sketchy. Barcelona has a much lower floor when it comes to quality of guys, but they both have the same ceiling.
David, my favorite from Barcelona was there. He said business is way down in Barcelona (I literally hired him at Thermas last month).
The facilities in Zurich are much nicer, and there is a nice nap area. But if you're visiting either city mainly to visit the saunas a few times, I agree with everyone here that Barcelona gives you more bang for your buck (pun intended).