Sure thing. Disclaimer: I’m not a powerlifter! So my experiences may not be super applicable to your needs. I’ll explain them in order I ran them.
915: This program made me feel tough. My work capacity improved and I felt less intimidated by heavier weights due to the supramax movements. That said, if I could go back to when I ran it I’d tell myself to drop my maxes the % are calculated from about 10lbs to make recovery a bit better. I’d also want a better conditioning base for the higher volume phase. Lastly I’d re-order the workout days as deadlifting before squatting in the week wreaked havoc on my low-back (user error). If I run this again I’ll need to make fatigue management a higher priority, sleep and diet could have been better.
BTS: Probably my favorite of the bunch. My technique improved and I learned to grind properly (no form breakdown) and to fail properly. I felt fresh for each training session and rarely sore. My physique was not ideal, but I attribute that to a complete lack of conditioning rather than the small amount of isolation/assistance work. My peak strength (1-3 reps) was at its highest, but 915 I think gave me better repeatable strength (4-6 reps). If I run it again I’ll be sure to include more conditioning work, and use body weight movements for assistance rather than isolation type work.
Optimal: This is a good program, perhaps my least favorite of the bunch, but that’s more on me rather than the program itself. I was actually planning on running 915 again when I saw this and decided to give it a try. I’ve gotten the best physique gains out of the three on this program, but my diet and conditioning have been better which is a huge factor. I don’t think my overall strength has changed too much, but hey, I don’t mind looking good! The biggest drawback for me personally is the frequency. I feel fresh for each session due to the low volume but it’s hard for me to get under the bar that often with other life obligations. I like and use supersets and giant sets, which allows me to get these workouts done in 30-45 minutes usually. I’d rather a little more volume per session and a day or two less per week. Again this is not the fault of the program rather it’s my personal preference.
Not sure if this will help much as there were some inconsistent factors and I don’t PL. That said, I did improve in some manner from each of them.