Some people swear by them. I personally do not prefer them. That said, I'll try to be objective.
In all, the pros of acrylic are:
- Might be a little clearer at first
- Drillable
- Lighter
- Less likely to leak
- Less likely to break from blunt force (being struck) Keepers of Mantis Shrimp like them as Mantis shrimp can break thin glass tanks.
- A better insulator
The pros of glass are:
-Very hard to scratch
-More forgiving of uneven support from the stand
-More open top (not usually euro-braced)
-Usually cheaper in larger sizes
The cons of acrylic are:
-Not durable. They scratch easily, and no matter what you do, you can't avoid all scratches. They WILL happen.
-Often made out of cheap acrylic by amateur houses, so watch where you buy from. Extruded acrylic will swell, distort, etc.
The cons of glass are:
- Very heavy.
- Seams can fail over time (but generally, as long as the tank doesn't go empty for a long time, the seams never dry out and last)
- Easier to break from being struck
- Not drillable in most cases.