If you throw out a couple of scam artist oils, all of the rest are pretty similar. For some unknown reason, I still feel that M1 is one of the best out there, but have absolutely no evidence to back it up. On my tractors, that have hydrostats that take some work to change, I only trust them to M1 15w50. Aside from that, I use ST, Mag1, AZ, Oreilly's, AA, RK, Traveller's plus all the major brands, pretty much interchangably. I just don't see any major differences in brand. I do tend to stick w/ syn in all three cars, not based on any need, but that it's usually only a few dollars more than conventional.
Just to show I'm serious, my 2008 PT Cruiser has 5w30 QSUD in it now, my 2013 Altima has RK 0w20 syn ($2.59@qt, hard to beat), and my 2010 Tacoma has PPPP 5w20.