It’s a good idea to think of aquarium size in terms of the aquarium setup as a whole. While that includes the number of gallons and water volume, it also includes size and area considerations including:
The actual aquarium dimensions;
Room for the aquarium along with the stand or cabinet and hood or canopy;
Space between the back of the aquarium and the wall; and
The amount of free area around the front, sides and above the tank.
Adequate space around the tank is important. If the tank is too large for the room or placed in a high traffic area, that could lead to disaster should something hit and break the glass, like a vacuum cleaner handle or broom. Glass is strong but it's also fragile.
Along those lines, pay particular attention to any shelving or hanging items in the space above the tank. It’s possible that something may fall off the shelf or the wall, and hit the tank glass just right. The next thing you know you’re in buckets, towels and squeegee mode…not to mention it could be fatal to the fish.
Another important consideration is to make sure the aquarium size allows for enough room between the back of the tank and the wall. Make sure to provide space for accessories such as a power filter or canister filter, air hoses and water hoses, a digital timer and electrical plugs…not to mention the aquarium stand or cabinet itself. And be sure to account for the space needed to reach around the back of the setup to clean and maintain the tank.
As far as stands go, be sure to select a stand with enough inside height to adequately store your filtration system. Protein skimmers and UV sterilizers can be quite tall, so be sure to take that into consideration when choosing or building your stand.