I remember looking at that site and this tank when i was deciding on what i wanted as far as tanks go. Did a crap load of research, probably the saem as your doing. If i remeber right I didnt like thier warrenty policy or it wasnt up to par of the other tank manufatures.
IMO, the 3/4" will suffice for a simple reef setup with sump and a returm pump with Powerheads for additiona circulation (and/or closed loop).
If you plan putting in some sort wave making devices, where water will shift some weight around inside the tank i would think of going thicker.
Call them and tell them your plans for the tank and talk to them about warranty coverage.
The better the coverage the better they stand behind thier craftsmanship.