It kind of depends on what you want and how you want it to look. For the most part, glass tanks are going to be strictly rectangular. Bow fronts and wave tanks will have to be acrylic to get the bend with a few exceptions. Both of my 29 & 75 gallon tanks are glass while the smaller 2.5 and 5 gallon ones are acrylic. One thing you have to be careful of with acrylic is scratching, especially if you have a sand substrate. If you use one of the magnets to clean and get a piece of sand between it and the glass, you can do pretty serious damage and not realize until it's too late.