What do you guys think will put on the most lean muscle mass, which do you feel is more effective for long term mass?
I have done both.
HST seemed more effective for me when I was smaller, but as I have gotten bigger, stronger, and increased my ability to stim my muscles, I would have to say Starr has produced the most massive strength gains in 4 weeks for me. Honestly, if you follow the Starr 5x5 program, increasing your max 5x5 lift (pyramid up weight and static weight sets) by 2.5-5% in week 4 is great!
HST is good, esp if your workouts need to be 30-40min, but the composition and strength changes are just more massive with Starr.
Where HST fails and Starr shines IMO is the periodization (increasing and decreasing) of weight within the same week, for squats. Squatting 3 times a week has made a remarkable difference in my physique. Where as HST has you squat 3x a week, it is only for ONE set. Starr has you squat 3x a week for 5 sets (5x5 static weight, 5x5 70% static weight, 5x5 Ramp up in weight).
So...in case I did not specifically answer your question - Starr is superior.