All brand changes formula due to API spec changes or cost/supply issues, so I don't see a point of sticking to one brand. Even Johnny told us before that there are 2 types of base stock used in YB (GRP II+ and GRP II / GRP III blend). So IMO as long as you are happy with what you buy just use it.
For me, Valvoline because they are the ones that give out double rebates most often (from Kragen and Valvoline), so I got them almost for free. But if I am buying when not on sale, YB would be my choice, and not Mobil (I remember they used sodium as additive and could hide head gasket leak if happened).
Of course, supporting Johnny along the way is good too.