Most of my buddies use Titegroup; I use HS6 because it is what I had on hand when I started loading for competition and have just never switched yet to date.
What I have noted about HS6 (I use 4.7gr in the summer and 4.8gr in the winter):
-Probably because it is a heavier charge weight, the velocity can be more finely tuned and exhibits lesser extreme spread, since each tenth of a grain accounts for a smaller percentage of the total velocity vs. a fast powder like Titegroup.
-I suspect it is better optimized powder for higher pressure loads, and that it is not really burning fully in minor loads, leading to a dirty gun. My buddy and I shot our G34s for ~500rds each in a class one time not long ago, and directly comparing them afterward, his (with Titegroup) had the slide move just as freely as mine does when it is clean. Mine was notably sluggish, and I start to get occassional short strokes at that round count until I clean it.
-I have never shot a minor load that feels softer than my HS6 load.
From what I can see Titegroup is slightly snappier, much cleaner burning, and slightly more economical than HS6.
I am actually getting ready to do some load testing with Titegroup since I'm getting ready to try out a different gun anyway.