I was looking at buying a big apple. I found a 20×2.15 (55-406) on sale, but they don’t have the thinnest big apple 20×2.00 (50-406). Do you think there would be any noticeable difference in performance between the two?

As long as it doesn't cause frame or fender clearance issues, I think you would notice minimal, if any difference.

I use the 2" version and ride on some of the nastiest cobbled streets you can imagine, they are unrideable on my 700cx32 . The 2" are fine and I cant see the need for anything wider unless it is for a really heavy rider.

Ok i ordered a big apple to see how it does.
Thank you so much for the input