How does the rate of restenosis of coronary arteries compare with medical therapy over stents?

Not sure. I am not sure what is meant here. If there was no stent or balloon angioplasty to begin with, the term "restenosis" is sort of irrelevant here. On the other hand, if one is talking about treating in-instent restenosis with medical therapy; if the patient is asymptomatic, there is no reason to not try medical therapy for a while at least.