A cloth ligature will stretch over time, but over a LONG time. I've found that as long as you are comparing decent ligatures, they will not have a noticable effect on your sound. On the response and feel of the mouthpiece, a little. The great thing about Rovners and their kind is they are consistent, easy to use, and inexpensive. And you can drop them and not worry -- doesn't sound like a huge advantage, but try that with a Bay. That said, I don't use them. I settled on a Beechler, because I felt it gave my tenor piece (SR fusion) quicker response. But you're talking about very subjective differences. If your Rovner dark works for you now, don't sweat it.