Coke or Pepsi... same deal.
I'm a fan of glass for the simple fact that if you need to clean it in a hurry a razor blade rules your world, while they do make acrylic safe scrapers and what not none of them are anywhere in the same league as a razor blade.
That said it's not a waste to put acrylic in wall either. I wouldn't go with 3 sides blue, maybe put an external blue sheet up if you want that, for the simple fact that 1) when you're working behind the tank being able to see through the sides/back is nice, and 2) it will get covered in coraline algae, so why bother with blue, either wait and give it time and have a purple wall, or call it maintenance and clean those walls too when you want.
External overflow certainly is nice, but only if it's done right, if it's simply a couple round holes drilled on the inside that goes to a box on the outside that isn't done right. Also look into something like the Synergy Reef overflow box, it's a bit of a pricey option, but it is very low profile in the tank.
