I think there are no speed benefits to be had. Maybe even a little loss. But there are other benefits of the MT’s and multi-blade props. As mentioned vibration and noise. But one of the better ones is during prop strike or crash. Look at these photos of a Turbo Commander that came off runway and had prop strike at a small grass field in Idaho. The MT props splintered and didn’t penetrate or damage anything. And probably put less strain on the gearbox than a metal prop would have.
Unbelievably, that aircraft was field repaired with new props and flown out of there in less than a few weeks.
