why not the best of both worlds?
I just picked up a custom tank. It is 12'x30"x30". The back, two sides and bottom is 3/4" black acrylic. The top has a typical euro bracing. The front panel is framed with 2" black acrylic that is bonded to the sides, bottom and top euro bracing. Inside the acrylic frame is 3/4" starfire glass. This is one of the best designed aquariums I have seen. When the tank is filled with water, the water pressure actually pushes the glass against the 2" frame thus sealing it even better.
It took 6 of us to move this beast using furniture dollies, hydraulic lift and plenty of suction cups. If acrylic is lighter, its not much lighter.