I have 5 different mats and they all sound different. Even the two mats that are made of felt sound different from each other. The mats are also all different thicknesses, so there is that. Even though I have the capability to adjust VTA on my head-shell, it is cumbersome, so I set it to sound best at a certain height above my platter and then substitute different mats for different records to achieve that approximate height by looking at where the record sits relative to the spindle. I await the lecture on the small difference in cantilever angle that changes in height of the record at the platter will make. I know what I hear, and it makes a difference to me, although some cartridges seem much more sensitive to VTA than others.
YMMV
kn