glass all the way. stiffer, harder to scratch (although not impossible i have found lol). ok so heavier, but really, in the grand scheme of things, you got 125gallons of water, rock, etc. thats 1200odd lbs of weight right there, really, whats the few extra pounds saved by plastic? just my opinion.
if money no object though, id go custom. using starfire glass, which gives you much better clarity than regular glass. rivals acrylic i think. few manufacturers using it now too.
heck if i could find someone who could do it, a 120gall wave front tank would be awsome. would be some major custom work though.. but money no object
thats my dream anyway.