I always get amsoil. Theres tons of interesting torture tests and spec verifications of all oil brands and types on youtube. Amsoil almost always come out as the winner. Its usually Amsoil and Pennsoil that come out on top.
Its not hard to get, so why not.
I do know one thing ive noticed with their severe gear oil line. When i started using it in my diffs a long while ago, on all my vehicles, the amount of powdered metal particles on the drain plug magnets dropped to almost nothing. That to me was a very good indicator of its protection.
Its not engine oil related to your question, but they do seem to make a significantly higher quality oil.