fiberglass enclosures

I have seen fiberglass referenced as a building material when people wanted to build spheres or exotic (to me) sandwhiches of different components.
My question is this: what is wrong with plain fiberglass for an enclosure? Does it resonate when it is .5" thick ?
Is it jsut that it is much harder to work with than MDF that it is ignored or is it inferior to MDF ??
I wouldn't bother with it for flat panels but for curved shapes it would probably be useful.

I can envision the process of making a parabolic shaped enclosure with a wood veneer exterior. Personally, I'd lay up the fiberglass to 3/4" rather than 1/2" for larger floor standers but I'm sure 1/2" would be sufficient for satellite enclosures.
working on a box with curved sides (a la Sonus Faber Amati and Wilson Benesch Act 2) see links to "lots of questions", "making a dead cabinet" and "bending wood".

I am now toying with the idea of making a MDF-fiberglass sandwich. willl it be any good?

Dave (planet 10) I think recomended using ply if I can work with it. He also reomended that I drop using lead as in a MDF sandwich (wonder why).

So it might seem that I will try using 4 or 6mm ply and see if that bends any easier.

does a ply/MDF - fiberglass sandwich make sense?