It's odd. A couple of years ago I did a little test, 3 tanks of what was E5, 3 tanks of premium & 3 tanks of supermarket petrol (E5) and just did my normal things on the bike. I didn't think there was much difference between them all. A couple of mpg more on the premium, and it was a couple, but I didn't think there was anything different about the 'feel' of the engine.
However with that Esso stuff I was pretty sure I felt a difference & not just with the mpg.
Interestingly since I've been using E10, the good lady has asked, on a couple of occasions, "what gear are you in?" and when I said "why" she has responded that she thought the bike was vibrating more than it does for the speed we were 'cruising' at. (I hadn't noticed anything)
She hasn't been on the back since I filled up the other day so I'm not going to tell her about my thoughts & see if she mentions it again.