My opinion, would be glass. Like the stated obvious reason that it is more scratch resistant. I didn't see it mentioned earlier but also with glass, if you're using non-tempered, the thicker it gets the more green it begins to shadow. I'm assuming this build will be with about 1/2" thickness or more. That's when most opt to use starphire glass because it's allows more light to pass through and gives a clearer view but that's gonna run the bill up more. Personally, I plan to use starphire on the front panel and side panels of my 200 Gallon build. Then use non-tempered on the bottom and back since their won't be any viewing from there of course. The bottom panel being 1" thick for more support. Acrylic does allow a little more bending, but like also mentioned, can be scratched fairly easy and not all scratches can be repaired. I'm not to sure about the shadowing in acrylic but I would assume there's not much an issue because i've never heard of anyone saying that they had that problem. Glass also weighs more than acrylic. So, acrylic could be a good option for you on such a big build. But my best advice would be to gather all this info and make a decisions based to your needs.