Ewan ko lang mga dudes.
I've own one great sounding plywood guitar (a Juno MIJ strat) and one OK-sounding plywood guitar (an Epi(phone) strat).
Yung Juno was an impulse purchase. It sounded so good on a big amp sa Pier. I said ...teka...yung amp siguro yan. So I had it plugged into a small 10watt Ibanez amp and it still sounded great. So out of craziness, I plucked out the 4k for the guitar which was meant to be spent on something else and got the thing. When I got home to examine it, potek, plywood.
Ditto with my Epiphone Special II LP. It sounded better than my RJ solid-mahogany Goldtop. When I examined it, it was also made of plywood. I traded that one for a Boss ME30...some part of me still regrets parting with that guitar.
My Epiphone strat naman was "OK" when I got it in 1994. It was still just "OK" even as I changed its pickups to various configurations. It was also plywood.
So without straining too much over it, there are still some variables that I guess we don't have the answer to yet. Like with a chat with Arie, he was telling me about these luthiers who found this 50-year old slab of ...what was it...I think it was ash. They made 10 guitars out of it, of which only 2 turned out well. And that's from the same slab of old wood !
I will agree with one thing about plywood guitars though. You will have longevity issues. In time the layers will come off one by one, due to the natural humidity of this country. Hardly will a plywood guitar turn out to be an heirloom. But as for the sound...we can never tell until you play any specific guitar.
Teka...other guitars were made out of non-wood materials like the Abel axe, RJ's transparent resin guitars and if I remember correctly, SRV also owned a strat that had a solid marble body. The latter had monster sustain because the marble did not absorb any of the string vibrations