I like glass over acrylic, but you should thing about a possible euro brace of some sort for support cause 5' is pretty long whiteout any sort of brace
I have had both. Acrylic was much lighter but the scratches drove me nuts. I love my Red Sea Reefer 350 but it is quite a bit smaller than you want. I don't think I would buy acrylic again unless that was my only option in the size I wanted.