I work with both acrylic and glass aquariums all day long. My advice, if you're planning on doing a reef tank especially is to not do acrylic -- go glass. Acrylic can scratch so very, very easily. While it is repairable, you don't want to constantly be doing that. :-D
A reef tank is going to have a lot of rock and coral in it that can topple and scratch the acrylic. Some of the animals you put in there may do so, as well. But, the BIG thing, the number one reason I say to do glass for a reef tank is that you WILL grow algae on the acrylic. This is not your normal "oh, look, a spot of algae, let me wipe it with my finger" type of algae, but you'll get some of the Dot Algae, Coraline Algae, etc. that you need to actually really work to remove. There are plastic safe scrapers (like the "red blade" from Kent) that work, but in a deeper tank, they're a pain in the butt, and you'll really have to be patient and take your time to remove them. I Have a 30" deep acrylic reef tank in service, and it takes me 2-3 hours to scrape it. It is probably about 24" on each side, so it is not that big. But, I have to take the time to get each little spot of algae. I have larger glass reef aquaria that take much less, because of a new invention that removes even the toughest algae on glass in seconds. It's called a razor blade.
Go with glass. You'll be happier.