In my experience, if you can tell the difference the felt side is smoother. The wire side can have a pattern strong enough that even though you don't see it may cause moire by conflicting with one of the AM screen angles.
Of course changing the question slightly can change the answer. Attached is what the Romano father and son team have to say on the topic. This is from the GATF Encyclopedia of Graphic Communications a book thick enough to stun an ox.