As far as I know, they both perform about the same.The cement board is
exactly that- fiberglass mesh with cement sandwitched in the middle. The
hardy board is a fiber and cement product with other waterproofing
I switched to the hardy bd, it is lighter(easier on the back), less
likely to crack and crumble apart. I cut it with a circular saw w/ an old
dull carbide blade,which goes pretty quick and makes less dust than cement
bd.The hardy bd installs with screws or nails more readily than cement brd.
Its a pretty good product, I don't float any walls anymore, or countertops
either. The only fresh cement I use now is for shower floors in order to
create pitch toward the drain.