I'd rather take my chances under a 'chute than trying to land in a 'black bit'
Hmmm, I would rather do it the other way. I fee far safer inside the plane, even when things are going wrong. As long as the aircraft can be flown, it can be landed, There's as much lift in black air, as illuminated air, you just can't see it as easily!
The structure of the plane is designed to protect you. Unless you're wearing body armour under the 'chute, you're better off to stay inside the plane. Though it may end up returning to earth in an unsuitable area, when you "land" the plane, there's a very good chance you'll have a working landing light, I doubt your parachute has one!
As has been mentioned, it's really hard to get out of most GA aircraft in flight. It's unlikely that when flying with good airmanship, you'll ever be in a situation where a 'chute would be the better choice (and I'm biting my tongue hard not to not get back into denegrating the ballistic 'chutes on some planes).
We GA pilots have generally been trained to fly, not to "fly or flee". I presume there as a military pilot training element which includes the decision making appropriate to decide fly or flee, at any given moment when things aren't going well. For us civil pilots, I think it's more a case of make the best of what you've got.
When I flew jumpers, I was required to wear a chute. This was only a requirement bacause once a pilot died, becaue he too was flung out of a plane when control was lost on jump run. I suppose there is also the concern of a jumper hitting the tail, and jeopardizing the control of the aircraft, but that was unheard of, when I asked.
Don't worry about wearing the 'chute when flying GA. It's kinda like wearing a helmet in similar flying circumstances, it makes people wonder what you're thinking.
I got the impression that engine fires/failures were pretty common
Nah, not really... I've had four, in 6100 hours of flying. Each time I landed without damage, and in a place, from which a later takeoff was possible. Yes, there's a lot of luck in that, but some careful flying too. Plan for engine failures, but don't worry about them, it spoils your flight.....