This topic has been thrashed out many times on here and as far as I know there has never been a consensus.
Oil, as long as the spec is correct for the vehicle is oil. The differences between grades and manufacturers is not as much as many people think. I used to work for Caltex (a joint venture between Texaco and Chevron) here in NZ and we used to sell a lot of oil. A lot of it was the same stuff in different bottles; for example we used to sell a general, cheap, put in your oil can to stop the door hinges squeaking type and another very expensive bespoke blend specified for a certain model of air compressor..... It was the same stuff!
That being said there is an additive called ZDDP that is important for lubricating the camshaft and the flat tappets in an engine. Basically it is zinc. There are of course a lot of other secret herbs and spices that oil companies put into their oils for specific reasons, but again, the difference between brands is not that much.
The moral of this story is that as long as the oil you get has the right viscosity, and the right additive package it will be fine.
My two cents
Chris