+1 What SNAKEYE said. EITHER of those will work well in 9mm. I have no actual experience with Titegroup, but wouldn't be surprised to learn that it works well. HP-38 and W231 are one in the same, so I'm not sure it'd be an improvement.
I don't own or shoot a SMG (darn it), but what I GATHER is that powders which burn at the rate of Unique or faster seem to work better. With this said, I'm going to offer contradictory advice & suggest you explore using AA#5 for some SMG loads. Meters well, burns, clean, and likes being pushed hard. If you load for your SMG to a power level just high enough to reliably operate the bolt, you may NOT like how it works. If you must load fairly hot, anyway, to obtain reliable functioning, then trying AA#5 might be worth it.
I find it heartening to learn that Unique works well in SMGs, but I would have thought the preference would have been for one of the newer ball powders (I'M thinking of AA#5, here, but I could see WW231 working, also).
I guess, with a blow-back SMG, it's difficult to see much velocity increase with slower-burning powders, but I've always wondered if the difference was more than what could be expected from random factors. In a roller-delayed SMG, perhaps the difference would be more pronounced. If such an SMG is built that would accommodate a 10mm or 9x25 Dillon, the shorter range limitation associated with weapons of this class might need to be rethought.