Zell is okay. I like Bullay a little better, mostly for its location and transport connections. It's a small town on the river with a ferry to Alf on the other side. From there there are several very nice walks/hikes. You can also bike from Bullay to Zell - it's only 4 km or so as I recall - along the paved Mosel River bike path most of the way.
We stayed in a nice B&B - Gästehaus Eberhard - a block or two from the town square with balcony and partial view of the river. Had an outstanding breakfast.
A double goes for 18 Euros per person, a little more for shorter stays; site is in German but photos are here:
www.gaestehaus-eberhard.de/gaestehaus.htm
(Don't tell Rick about the place, or the prices will go up!)