Sure would be nice if you could try out a few. Like Daddy Bear, I prefer smaller risers/grips and have a few GN Ghosts and Critter Gitters and some Hills. I agree that the small TD grip is close to the size of a CG grip, but it's smaller than a standard Hill grip, which is usually about 2 inches deep back to belly, give or take a little. The larger t/d sleeve would be closer to the standard Hill grip size.
Sometimes sleeve size may be somewhat dictated by bow draw weight, i.e., a heavy draw weight bow requires thicker laminations. Now the riser can be slimmed down to still accommodate a small sleeve, but it may not be as aesthetically pleasing. Generally, a larger sleeve will be stronger because it retains more of the riser wood within the sleeve.
The T/D sleeve will add about 6-8 ounces or so to the riser weight. Most folks like that. Gives a little more heft to what normally is a very physically light bow.
All in all, it boils down to personal choice. Either size will work. Good luck.