I'm no expert but I've played with different octanes. (Next step will be brand of fuel. It's all the same stuff but their additives can vary.) So I tried 'em all from 87-93.
For me and my 2001 VT1100C it's a toss up between 87 and 89. If I could run 88 that would probably be perfect. The vibration at 70mph is almost non existant with the 87 but I think she starts a little rougher. I'm still getting to know her cold, warm and hot starts so it could be me. There's definitely a noticeable difference in the vibration with the 89 octane.
I just started to watch gas mileage now. Might be losing some with the 87 octane. Will advise...
It's not the destination...It's all about the ride!