I use PB Blaster because it works, it's relatively cheap, and it's easy enough to find.
When I was a unit armorer (86-87), I used to look after a small vault full of guns: (100 M16A1, 5 M203, 25 M1911A1, 5 M2HB, 2 M-60) Breakfree CLP was the potion du jour. FWIW I cleaned my junk (and the motorpool & mess sections' M2HBs) by soaking with carb cleaner spray, then hit em with the Steam Jennie, chased the water out with WD40, then a coating of CLP back in the vault. As stated, it is near impossible to get a gun 'white-rag' clean using Breakfree, in fact the -10 manual for the M16 addresses this as not a bad thing...just the way it worked. FWIW #2, I have found it at WalMart and bought a small bottle (nostalgia?) on my own guns I use #9 solvent and lube oil.
PB Blaster does a great job, and if something defies me after using it a few times, IMHO it's usually time for the hot wrench.