I think theres advantages to either but glass probably edges out acrylic for a plywood tank.
So you want a 1000-2000 gallon tank? Something like a 10'x5'x5' with a roughly 8x4 viewing panel? I think youre gonna want to play it safe and go with 25mm (1") glass, though 3/4" tempered may cut it. Ive never built that big i would peruse some of the larger builds on here if i were you.
Same thing with acrylic. 1 1/4" would be foolproof at that size but 1" would probably work too.
Lepisosteus
for further insight perhaps...