If you were to collide with unwelcoming terrain, the more substantial fuselage structure and skin of an airplane would offer much greater occupant protection. To me that is an equally important "strong". You can nearly always control how many "G's" you're pulling, you may not always be able to control what you're going to hit!
Well a pure straight CFIT will probably kill you no matter what you are in.
However, you need to remember that microilghts have very little momentum and that plays a big factor in the surviveability during accidents. Speaking from a 3 axis point of view, a microlight would come out well ahead of the average cessna or piper single in for example engine failure after take-off situations - the low stall speed and low momentum of the microlight coupled with the 4 or 5 point harness that most have plus minimal amounts of alluminium to hit you as it caves in.
Do you really think that the crappy inertia reel single shoulder strap which only locks properly 60% of the time is going to prevent your nose finding it's way into the internals of the altimeter should the Cessna or piper you are flying come to a very immediate stop?
There is much more to it than that of course but the more you check the more you will find that simple, slow low inertia aircraft well designed, well certified and well equipped from a safety point of view (4 or 5 point harness) wil win every time.
Overall, one can not discount a properly maintained and certified microlight on strength or safety grounds.
Regards,
DFC