Which is better adhesive or mourter for applying ceramic tile on cement board floor?

I would use canned adhesive that you spread with a trowel. It is more uniform. Does not break down like morter will, since morter has sand products in it. Besides, ceramic tile usually has spacing that will be filled in by grout, but some actually s up together, and some comes already attached to a mesh backing. I believe adhesives that are on the market are much better than morter. In addition, adhesives have better holding power, even on cement board flooring, as long as when you trowel it in, you ure you apply pressure on the trowel to force the adhesive into the cement board matrix.