If I violated NDA's I've signed, I could show you proof that not all oils are equal in a racing application. Of course the racing application is much more demanding than any street legal engine. It would show that some oils do protect better than others.
In my shared-sump motorcycles, some oils definitely perform better, primarily in shifting characteristics, and ability to maintain slick shifting.
In some LSR bikes I've worked on, some oils did a better job protecting the transmission gears. So we used the oils that protected better. They did happen to be more expensive.
If you can discern no difference in oils run in your bike, then by all means run the cheapest.
I have replaced gears with wear lines on the tranny teeth, this with 20w50 motorcycle group 3 oils , it wasnt all the gears, just one, top 6th gear. I have a magnet on drain bolt, and I know for a fact, its all gear wear spooge I get on that magnet.
I would think it would be hard to better that with any other oil, but maybe there is?
Same oil, excellent cylinder and ring wear, like none , now, this is not a 3 ring piston design, but super tiny oil ring ports that tend to start clogging after 600 hours, be nice a fix for that, and maintain the lack of cylinder and top end wear.
Right now, Im running some 10w50 Maxima pro plus, just to see if worth the cost, and it would take alot of time, to really get the data I already have on the other oil. Shifting wise/ clutch wise its solid. I actually thought it was quite overly slick but seems to have the necessary clutch bite.
Those are the two items Id like to reduce, oil ring carbon build up after hundereds of hours, and gear teeth wear lines.
now in another bike I ran group 4 pao in a 5w40, and it still generated tranny meatal spooge, just like i see now.
So I come back to how much can another oil really make a differnce in those two areas.
I know a high viscosity is needed on the tranny , but that can have negative benefits with tiny oil ring ports in the top end.