Because the velour is better defined, and clearer, the treble is easier to pay attention to, which is why it may sound more grating to you.
This is a case of clarity being a downside... to some people. You're simply more used to the veil the pleather has over the velour.
There is a similar amount of treble on both, but the pleather has a sharp rise from the upper mids to it's treble peak, whereas the velour has a stronger upper mid response that gradually meets the treble peak in comparison. So in the case of add some, lose some, the balance between bass, mids, treble, is more linear on the velour. You have to remember, when you add something, you take away from something else. Or when you take away, from something, you add somewhere else.
Less bass = more mids or treble
More bass = less mids or trebles more bass. You're compensating the lack of upper mids with volume. I'm surprised the treble isn't destroying your ears.
Edited by Mad Lust Envy - 10/13/13 at 12:57am