I buy oil based largely on price.
This sometimes gets you M1, sometimes PP, and sometimes either GC or Edge.
Once in a while, I have found things like the old Rotella 5W-40 on closeout.
For those who really prefer SOPUS, there is no shortage of deals on oil brands from them. The majority of the oils in my stash at the moment are SOPUS products, with some Castrol (Syntec and GTX), Chevron, Valvoline and Mobil (M1 and Delvac).