Installing Heated Floor on Concrete Basement Floor

I am installing an electric heated floor on top of a concrete pad in a basement which ceramic tiles will then be placed overtop. I have been told that I should insulate the heating floor system from the concrete pad to prevent heat loss down into the pad and encourage it to move up into the tiles. A couple options considered are:

1. Install 1/4 inch cork by thin-setting it to the concrete pad, then installing the heating system by fastening it to the concrete pad (through the cork), followed by applying a self-leveling mortar over the cork and heating system and finally tiling over top that.

2. Lay down a vapour barrier overtop the concrete pad, then fasten 3/4 inch plywood using a Ramset to the concrete pad (through the vapor barrier), then install the heating system to the plywood, followed by applying the self-leveling mortar over top the heating system and plywood and finally installing the tiles over top that.

Does one system sound better then the other? Any suggestions?

Thanks,

Mark.