I've had my acrylic tanks for about 4 years and they're are as clear as the day I got them, also acrylic is way clearier then glass even the starfire glass that some people use. Because it was so clear I was able to use less lights, even though it was a much bigger tank, height was an additional 1', and the tanks looked brightier and it actually glowed.
One you go acrylic from the look of it you'll never want a glass tank again.
By the way you can stratch glass also and unlike acrylic you can't take out the scratches.