I've tried the higher octane stuff in every vehicle I've owned to see if it makes any difference (there's been a few), I've found more often than not it makes a difference in the ones that it shouldn't and vice versa. Examples: My ZX7R, fixed timing (though a +4 advancer fitted) - much smoother on part throttle\load. Hornet 900, fixed, better MPG. Pug 106, always 15% better mileage. Beemer 3 series w/knock sensor\advancer, handbook said recommended to run on 98\Optimax\V-Power (or whatever Shell were calling it at the time) = no difference whatsoever.
All tests done same commuting routes, variety of roads, same general pace over at least 6 months. At least 5 tanks of each tested in a row of each RON before changing. Any difference was noticed within a tankful on all vehicles.
Not done any meaningful testing on the 10 but so far I can't see any difference.
I also use Shell all the time and never had a problem with the quality.