Man this reminds me of this one time when I went to college in Providence, RI.
I always knew that acryllic scratches easily, due to the fact that I use to own an acryllic device (I would rather not discuss its' use over here, but that it held water in it also) and it always scratched when I had to clean it. Even on a normal sponge, the rough side will produce very slight scratches. Thats why I usually prefer glass.
So anyways, my roomates decided that they wanted to have fish tanks, so i decided to tag along and see what was up. One kid was looking at tanks and he picks out an acryllic one, and I tell him that its gonna scratch so damn easily. He didnt listen to me. Well initially I wasnt going to get something but once I saw some small-aquarium-sized catfish, I couldnt hold myself back. Anyways I got myself a glass tank and you could compare the wear to the tanks as soon as we got back to our dorm room. by the 2nd month i had 2 small scratches on my tank but the kid's tank was scratched as hell. And most of it was done by his own fish.
So yeah, glass over acryllic any day.