I would only ever use synthetic clay on vehicles who's paint is almost already in perfect condition or has very little contaminants, on vehicles that have heavy contaminants "I" prefer real clay ...
While most of the synthetic clays are way less aggressive than the clays, you can still mar up the paint very quickly if there is a lot of contaminants on a vehicle, the reason clay is a lot better is because those contaminants embed themselves into the clay and on the synthetic clay they are floating around and if the person doing the claying is not careful and they don't rinse that towel enough they are going to seriously damage their paint ...
These towels are perfect for vehicles that are maintained on a weekly basis to prevent contaminant build up .....
But like you said
@Treburkulosis it is a feel thing, I personally do not like using them and try not to ...