Oil is always a touchy subject and in most cases there is no one right answer or best oil. Many people have found a particular oil that works well for them, and if that is the case then there is no reason to change.
With my racing I used to be sponsored by Maxima and never had a problem with their oils. Since those days I have tried all sorts of oils, and sent many used oil samples to blackstone labs for analysis. My findings have been that some of the more expensive boutique "motorcycle specific" oils, even the "high performance" ones are actually hold up much worse than some cheaper readily available oils.
For example, $11/quart Yamalube 4R (the oil that Yamaha recommends for their high performance street bikes and race bikes) fell from a 40 weight to a 20 weight after only 2 hours of hard track riding at race pace. Obviously that is going to be much harder on oil than street riding, but many other oils I tested did not sheer out of the 40 weight range that quickly.
Of the few I have tested, Maxima Max4 and Shell Rotella (both conventional and synthetic) have held up very well according the Blackstone. I was surprised to see how well the Super Tech diesel oil I tried held up as well.
For me, I have actually been running Shell Rotella T for the last 2 years in my vintage bikes as well as my modern race bikes. I like the zinc levels, I like the phosphorous levels, and I like all of the used oil analysis results I have been getting. The fact that it only costs $12 a gallon doesn't hurt either.
There are tons of good oils out there that would never cause any oil related damage to your engine though. My advice is if you are happy with what you are using and it isn't causing any issues, then don't change.
