Unique, but Trail Boss is getting some bench time now.
Yep.... Unique is one of those powders that I never seem to run out of, since it really does still cover a LOT of territory in my handgun loading. Trail Boss is kinda nice in the bigger cartridges, of which 45 Colt, on my bench, is the one with most capacity.
I'm happy with all that Unique will do for me, but I started to use Trail Boss a couple years ago just to give it a try, and if it does nothing else, it will prevent you from double charging just about anything.
I was hoping that it would produce more smoke, just for fun, like black powder, but oh, no, the stuff burns clean - not much smoke, not much crud. I did find out by experimenting that it seems to do well from 38 Special, .44 Special, .45 Colt, and since I load each, it's on my bench, too.
If I had to pick between the two, sign me up for Unique.