Cons Glass: Heavy, can crack, needs level surface, can leak, has more sealent
Pros Acrylic: Light, does not crack, does not need as much sealent, can be curved, retains heat sometimes, can block out some
uv light.
Pros Glass: Doesn't get scratched easily, Cheaper, more crystal clear, easy to clean
Cons Acrylic: Scratches easily, more expensive, depending on quality as not as clear as glass, harder to clean as most good scrubbers scratch
BTW: smaller aquariums are fine with acrylic but larger tanks are usually made of glass. I myself have a 24 gallon acrylic and it is fine. It has a curved front so it looks very nice.
Hope that helps.