The TT01-D has full ball-bearings, oil filled shocks, adjustable camber & toe, also comes with some anti-wear grease for the diffs. It's a very heavy metallic-like grease that tightens up the diff action so it acts more like a solid axle (good for drifting).

I've owned a basic TT01 and currently own a TT01-D and can tell you that the drift-spec kit is a much better bang for your buck.

Edit: Forgot to mention...the regular TT01 kit uses plastic bushings, friction shocks and has no camber & toe adjustability.