I own a D-nail Halo and had the opportunity to try a friend's TAG SiC dish recently.
The TAG dish is much thinner, and much smaller. The dish itself has less mass than the D-Nail Halo. The TAG doesn't retain as much heat due to thin ness (although to be honest SiC doesn't have huge heat retention capabilities, it's the heat transfer capabilities we care so much about) and the 'channel' that oil is dabbed into is MUCH thinner than the D-Nail Halo
TAG is also MUCH deeper, which makes it harder to get the dab on to the base of the dish. I would NOT put as big of a dab as I throw in my D-Nail SiC into the TAG SiC,: it's smaller in capacity, regardless of the "volume when filled". You simply don't "fill" a dabbing dish.. it's the surface area that counts and TAG's has a lot less.
Most of the time when my homie rolled up shatter balls to stick on the dabber and dab, the dab would hit both walls on the way in or the Nut which is more intrusive on the TAG design), and often, some oil would be lost going inside the nut or outside of the dish.
This simply does not EVER occur on the D-nail dish because its shape is more optimized; it is shorter, and wider, and has a much larger area to dab into without wasting your dab with oil "missed".
The homie had never considered the D nail brand equipment, but since I'd brought my gear along for a back to back comparison - once he used the D nail stuff and realized how much better the Slim series holds the Halo than his InfiniTi nail, and how much more 'dialed' the D nail components are, he's now looking to upgrade his TAG SiC set-up to D-Nail.
So, in short
@nosmoking I think there are far more advantages to the D-nail halo than you have guessed at, without having the opportunity to use both.