After reading about 80-85% of this thread (minaly the points by exnihilo and rajscorps), I came to the conclusion I thought I would:
We know that the discussion of which style of programs is best for size and/or strength can be continued forever with no clear "winner" or "end", which is why I even hesitate to post right now
I think the bottom line, in my time spent in the gym and researching, is: PL styles and HST methods seem to be interrelated and in some cases interdependant, although in the grand scheme of things a few general approaces are tweaked for each specific goal. I have been training with HST for almost a year now, natural and on-cycle. I have done typical 5 and 4 day split BB style workouts, HIT routines, GVT, and some modified 5x5 PL style lifting over the years.
My conclusion is that after researching it at length, and doing several cycles now, I am happier with HST than I have been with any other routine, but I am not a powerlifter, size is more important to me than how much I lift
After reading more about PL styles, however, one can see that concepts in HST such as SD and progressive load are commonly found in PL programs, just altered to suit strength needs, and may be focused differently as CNS adaption is still really the desired outcome.
As for HST trainees having the most gains in the low rep, high weight portion of the program, this is true. I would point out, however, that this seems to be a response to the progressive load (RBE) principle and the hypertrophy incurred for the first several weeks of the cycle, not IMO because it's just low reps, high weight. HIT training I have done used low rep ranges and high weight, but were not tailored with RBE and chronic stimuli in mind, needless to say the results were not nearly the same. Given a periodization shcme of HIT training, most seem to respond better to HIT style weight, which shows us what? That the progressive load concept is at play, which of course is stressed in HST.
I am simply saying that for everything I have read and tried HST gives me more growth vs. strength, which for me is desireable. Size is gained through PL routines of course (some PL's are huge guys, even at reasonable bf levels), but my recommendation to a trainee who wants to get bigger will not be a PL routine, simply because that is not the overall, specific focus, with all attention paid towards it. I do not believe that PL routines, all other things contant, will yield the same size gains in the same time frame as a periodized or HST style routine. After readin Haycock's work, I have yet to see anyone really go against it or show a better way to work with the 4 main principles for hypertrophy (size gain): RBE (progressive load), chronic stimuli, SD, and mechanical load. Just my 2 cents, and I am well aware that many could completely disagree with me here and continue the discussion forever.