A single engine GA aircraft can become a glider and safely land but while this is the normal behavior for the glider it counts as an accident for the plane. I'm not sure how you separate these categories without a tremendous amount of analysis.
GA aircraft can glide but they do it pretty poorly compared to a real glider. They have poor glide ratios meaning not much time to choose a field, and most can't feather their prop (because most of them are constant pitch) which makes it worse.
Also, a glider pilot is constantly aware of potentially needing to land and is trained to keep a lookout for suitable fields at all times. Most GA pilots will only start looking when their engine fails and thus wasting valuable altitude. Inexperienced pilots will also waste altitude trying to restart the engine before looking for a field. Which leads to hasty decisions. When gliding, altitude is fuel.
Glider pilots do "outfield" landings regularly, while GA pilots usually only practice the approach but not the actual landing. So they don't have nearly as much experience at it.
And gliders have super low stall speeds so they land more slowly leading to less damage/injuries if something does go wrong. And there's a lot less mass and no flammable fuel involved.
And almost all goiders have spoilers which are amazing for short field landings. They're basically an "off switch" for most of the wing. You have much more control over your descent that way and the flare is also much easier.
I think all these combined make for a much lower accident rate. I flew both gliders and GA aircraft :) If I have to set down in some random field I would hope to be in a glider!
So I don't think it's just a difference in categorisation.
I don't think there's any ambiguity in the question -- the asker simply wants to know whether gliders or GA aircraft have higher accident rates, injury rates or fatality rates, either per flight or per hour.
The fact that GA planes can glide doesn't seem relevant to that question. Or rather, its relevance is already going to be captured inside injury rates.
It sounds like the real problem answering the question is a lack of available data, which surprises me given my expectations of data around aviation accidents.
It’s an apples and oranges question. And as tows require a powered GA aircraft, and that’s the most dangerous part, it’s an apples, oranges AND apples+oranges question.
Not all gliding operations use tows. Winches are also an option. They're cheaper too but they are more limited in launch altitude.
There's other more dangerous things about gliding too, like the way gliders tend to bunch together circling to take advantage of thermals and get close to mountains to enjoy the updrafts there. So mid air collisions and controlled flight into terrain are more common.
But overall I'm pretty sure it's still a safer sport. But I have to admit I don't have stats either.
