Well, I don't like Rhino board much. It's very brittle. If you get too close to an edge with a fastener, it tends to split or break a chunk off. It's similar to Hardiboard...but Hardi is softer and doesn't break as easily. Not that I like Hardiboard either though.
The Protegga worked fine for me, but Ditra has a great track record and Schluter is a great company that stands behind it's products.
Still, all of the cement board products work well...Wonderboard, Hardiboard, Durock, Permabase...etc, etc. You really can't go wrong with what ever choice you make, because if you install them as directed, they do the job for you.
