I love the sound of the OS 90 with tuned pipe on the delta. Electric motors couldn't compete with that.
The 120 Four stroke in the Reactor Bipe sound awesome.
But I also like the sound of my electric hotliner, I guess there is a purpose for every motor.
Glow engines are on the decline, but I think they'll be around as long as we use them. I am Glad we do not have any noise restrictions and not going to stop flying glow engines.