I've often thought that it would be wise to carry a PLB while flying especially because ELTs have such a bad record in crashes. They rarely go off in the type of crash your friend was probably involved in.

I think the critical question is when does one declare an emergency. In general, it seems pilots are afraid to declare an emergency early enough for it to make a difference and in that regard I'm not sure a PLB would be treated any different than a verbal MayDay in the minds of most pilots. Still, I think carrying a PLB makes more sense than relying on the so often unreliable ELT alone. But then, all the technology in the world is not going to save a pilot from making incredibly stupid decisions like the pilot of your friend's airplane made.