Well, I don't know about useless. I have the tactical tanto and it's a great knife - takes a scary edge and holds it well. The push-button sheath is interesting, if not executed as well as it could be. But you're right that it's not really a utility knife. I should really put mine in the exchange pages.
I think that the Hissatsu is the inferior choice. It's designed by James Williams, and that's not really a name to argue with, but for the features offered, I think the tactical tanto is better. To list examples - the TT has a guard, while the Hissatsu doesn't. This isn't really an issue to me, though - Japanese sword and knifework usually treats guards as a fail-safe, rather than an active safety feature. The TT has a differentially hardened carbon steel blade, and the Hissatsu has an AUS-6 blade. The TT's handle is easily removed, and the tang is very well suited for customized handles. I like the push button sheath better than the plastic sheath for the Hissatsu.
Strikes against the Tactical Tanto:
- The blade is prone to staining, and the blueing comes off easily. I discovered the latter trying to fix the former. That sucked.
- The rayskin (real) isn't attached with much care. Mine has a small "crack" where the rayskin expanded, broke open, and exposed the wood underneath. All in all, a small problem that doesn't affect the fit of the handle to the tang.
- The oxidized black fittings and sheath scratch and scuff fairly easily.
Strikes against the Hissatsu:
- Stainless steel. I don't like stainless steel in anything other than a folding knife. And I hear the blade is being downgraded to 440A.
- Poor finish. The blade is supposed to be an osoraku-zukuri blade, but the execution is... lacking. The kissaki is a joke and the lines are all over the place. The TT is an odd shape, kind of shobu-zukuri based, but it's lines are much cleaner.
- Non-removeable handles. This may actually be a plus if maintenance is not something you like to do. Plastic is a cool material, though. It's not indestructible, though, and customizers would have a hard time with this knife.