No fay're! It's like you're asking me to choose my favorite child ( or in my case, my favorite cat)!
I love all three series, but the PS Upper Body has a special place in my heart. I go back to it time and time again when I want to split my routines. Matter of fact, I extrapolated shoulders, tri's, and bi's from it this morning.
2nd choice is Upper body Pyramid. Very time effective and I love the fact it's only dumbbells.
Still, I appreciate the slowness and preciseness of Slow & Heavy.
Oh, so many weight tapes, so little time!
Patricia