You also left out NASA at www.nasa-sports.com which is the fed I compete in.
To the best of my understanding it comes down to 2 basic things. How many ply gear is allowed and how strict is the drug testing (if there is drug testing at all)
NASA only allows single ply gear and its drug testing is very strict. USAPL is also single ply but I have heard numerous negative things about their organization, how they treat their lifters, and their questionable drug testing to name a few.
The IPF…to my understanding what everyone is trying to get too. IPF is actually an International Powerlifting organiztion. I also believe their gear is single ply, and that they have rules about which brands and such you can use. I could be incorrect here though.
As for the other feds I dont know too much about them other than they allow multiple ply equipment.
BTW, NASA has a multi-ply division as well and their drug testing, in my own experience, is no better than any other fed I’ve lifted in.
The IPF restricts gear based on whether or not the manufacturer pays them to have it on the “approved” list. For example, why is it that 20" Inzer wraps are allowed, but not 20" APT wraps?..because Inzer paid the IPF fee to have them “approved” for use in their fed. Kinda bullshit if ya ask me.
But, yeah, for the most part, fed differences boil down to testing and gear allowances. Also, some feds are regional. SLP is big in the midwest but not seen on the west coast at all. We have no IPF and very few USAPL meets here either. APF and IPA are big around here (Ohio).