I say glass is the best in our hobby. Not only dose acrylic yellow over time but it crazes (hair like crackling) around the edges. This i know of from the 600 gal. i restored at the LFS in NY. And then yes, you have a tank that scratchs easy, distorts from bowing and can melt over time too. The only good thing i can think of with acrylic is that any home body can drill it with a black and decker drill
They make good sumps though......