What is atherectomy's benefit over angioplasty, if it is in fact better?

Calcified blockages: Rotational atherectomy is used for very hard and calcified blockages. Its like a drill bit and strips away the calcium so an angioplasty or a stent can be deployed. Often without the atherectomy catheter u can't do a stent and a bypass would be neccessary.

It's probably not. : The argument behind atherectomy is that it actually can remove some of the plaque that causes a blockage. An angioplasty simply moves it out of the way. However, atherectomy can cause as much or more trauma to the artery and induce the formation of scar tissue. Surgeons and peripheral intervention must have been arguing about the merits of each approach for years.

Vs stent: Atherectomy decrease amount of plaque and the compliance of the plaque. Typically atherectomy is followed by angioplasty but at low pressure which may cause less dissection . In comparison angioplasty alone has more recurrence of stenosis and more dissection. Stenting have better patency and less recurrence but it eliminates target for future bypass.