Glass for sure. Acrylic will yellow/warp/scratch up over time where as glass will look much better for a lot longer.

I'm not sure on the basking shelf. I know that by default it is a single piece so the divider couldn't go in, but I'm sure AP could make one with a slot in it for the divider. You would have to take the top off the cage (very easy) to put the divider in or take it out.