To be absolutely honest, I discourage people from buying the poly case option.
I designed the board around aluminum levels of structural integrity; the lid has thin portions where it is sandwiched between the top and the weight.
We will be testing a poly lid to make sure it achieves the required levels of durability, but it is undeniable that it will be weaker than aluminum.
Polycarbonate threads are far more prone to stripping from overtightening screws, and the material scratches far easier.
The absolute mess of gaskets and foam on the interior will be visible.
Poly is known to yellow due to exposure to UV light. After many years, the board that was paid premium for may not look too pretty.
Anodized aluminum is much more durable and cheaper.
Sound-wise, with the plate fully isolated from the case via vibration-damping gaskets and the multiple foam midlayers, even aluminum won't sound cripplingly awful.
But then again, it is the buyer's choice, so as long as things reach the required durability, both options will be offered.
On the flipside, polycarbonate plates are a very nice option.