Acrylic weighs less, is stronger than glass (less 'cracks'), and usually lacks 90-degree corners or top/bottom frames...but acrylic also scratches more easily.
You may want to consider what size tank you're considering, what location and type of stand you have for it, and whether or not you like the look of rounded corners without top/bottom frames (acrylic) or if you like 90-degree corners with top/bottom frames (glass).
There isn't much difference functionally.
Good luck!