Tall fish look good in tall tanks. A tall tank with a given surface area will support the SAME number of fish as a short tank with the same surface area. Each gallon of water weighs 8.5 pounds. Make sure your floor can support the weight. Also ensure a stable platform.
Larger aquaria are subject to less fluctuation of temperature and water quality.
Get the largest you can afford. Choose a filtration system most appropriate for your fish and aquarium. In general, water should be turned over 3-5 times an hour depending on fish load. Determine size of heater. Submersible heaters, for the most part, are a better choice.