No, I don't really see a lot of difference. I don't remember what was going on back then but when I was originally experimenting with it the higher % alcohol was hard to find. Someone here mentioned wood alcohol, denatured, so I gave it a try and it worked. To me it was almost like spraying lacquer. This was before it was common knowledge that you could use lacquer thinner with it. But, lacquer thinner changes it's properties somewhat and isn't always what I want so for the most part, I just use denatured alcohol. To me at least, there was a notable difference between denatured alcohol and the lower percentage iso.
With X20A, if you reduced it just a little too much it would splatter and bead and run. With denatured I could thin the heck out of it and still get good coverage. May not be for everyone but it served my purposes. You can do the same with 91% or lacquer thinner. But, with lacquer thinner, it changes. You can't just get a little Windex on a brush or paper towel and wipe it away.