Which Type of Backerboard to Choose?

With backerboard, it's often more a matter of expense than needs. Backerboard (or tile backer, as it is sometimes called) is a solid, mineral-based substrate that you place under a ceramic or other tile (marble etc.) installation. It's far better than the ancient method of slopping on multiple layers of mortar. Wonderboard has one advantage over other types of tile backer in that it will...slightly bend. Yes, it does have some nice bendable properties, in the rare event you are constructing a curved wall. For that matter, HardiBacker or Georgia-Pacific's DensShield work better: easier to cut, cleaner to cut...less crumbly. DensShield even has mold resistant properties.

Note in this photo the plywood flooring, with backerboard installed just to the left.

Image Public Domain: U. of Washington