Glass wont scratch as eaisly, doesnt have to have as much support (larger tanks) because glass doesnt bow out, and AFAIK glass is clearer optically than acrylic.
Though Acrylic seams are WAY stronger, and it is way better at insulating than glass is, acrylic does hold up to shattering better than glass, but you can scratch it way eaiser than glass.....thats the main reason I like glass.