Not speaking for anyone else, but I personally think of the original 5/3/1 as more of a template, and the more recent versions as specifically prescribed workout routines. For this reason mainly, and its inherent flexibility I think 5/3/1 as originally written is golden.
Reason being, it allows you to set frequent PRs, it involves slow, maintainable progression, it’s highly FLEXIBLE, it is centered around big compound movements, and it allows regularly scheduled physical and mental breaks from tough training. These traits capture 100% of the value I get from the program.
For those reasons I will probably do some form of 5/3/1 for years to come, if not the rest of my life. Even right now while I’m recently more focused on physique than numbers, and doing more of a bodybuilding routine, the original 5/3/1 is the template and I just add auxiliary movements aimed at what body parts I’m trying to improve.
Sometimes I might do 4-5 singles with my training max after my last work set or I might drop the weight 20% and do 2-3 back-off sets for added volume, but I count those more as assistance exercises and adjust my auxiliary movements accordingly. And the best part is the template remains the same.
5/3/1.3 looks like a great program, but I was drawn to the simplicity and adaptability of the original that allows me to make my own program out of it. Anyone else in the same boat?