After all of this I do have to say, I don't think it matters what brand oil you use these days. Any synthetic will work the same as any other. There is a BIG difference between dino and synthetic, especially in the way they blend for multi-weight oils.
I do like to use at least the weights specified by the mfg. Especially in cold or short runs, use the lowest weight as gospel. 90% of engine wear occurs during start and warm up.
If you have an air cooled engine, the upper weight is important as well, especially during hot weather riding.
These days the metallurgy of the engines is so good that there is very little wear on any of the components. Unless the mfg screws up (like Guzzi recently did on cams) the engines will last for a LONG time with little wear. Heck, I had the heads off my 32yr old Guzzi two years ago and there was no perceptible wear in the cylinders at all (75k miles at that time IIRC). I could even make out some of the hone marks from the original mfg process.