Oceanic and All Glass Aquariums are both owned by Central Pet. They are one of the biggest distributors of all pet supplies in the country but they are HUGE on the west coast. I think the glass on the tanks are indistinguishable unless you special order sapphire glass from Oceanic which is extremely expensive since it doesn't have that green cast to it ( look at you aquarium glass from the edges).
The workmanship on the Oceanic tanks are nicer in terms of sloppy silicone work and more solid feeling stands. Most AGA stands are particle board while you can get oceanic stands in solid wood.
For my money, go with the AGA. Incidentally, the same company also own Island Aquarium. So AGA is really the middle of the road not the bottom