I saw a report once that said seat belts absolutely improve your odds in that situation:
(a) You are much more likely to remain conscious
(b) You are much less likely to become disoriented -- helpful if you need to smash your way out, but especially helpful because you don't waste time figuring out where the door handle is and which way is up.
I can see that.
Of course, if 1 can jump ship beforehand, so much the better. Never mind if you're strapped in an panicking, that can be a bad thing. Especially these modern belts with the difficult buttons. I'll take the easy button on the fat face of my old Lincoln anyday over the things recessed in the end faces.
I wonder how they come up with those odds. I still say it's all a conspiracy to limit your freedom. They never fail to mention about seat belts and they always buttress it as the end-all be-all.