Some really good points have been brought up in this thread--points to consider before purchasing any large tank.
1) Tank height and width. After a certain height/width, getting the tank through a standard door opening could become a problem. Taller tanks will require thicker acrylic, driving up the cost. Taller tanks make accessing the floor of the tank harder.
2) Maintenance of the bigger tank. Drip system or water changes? How easy/difficult will it be to do water changes? It would be a no go for me if I had to do water changes with a Python on my 300 gallon tank. Substrate or bare floor? It would also be a no for me if I had to stand on a ladder vacuuming substrate all the time. Call me lazy, but if it isn't easy and simple, it's not going to happen around here. We were fortunate that we were able to convert the furnace room behind the tank into a small equipment room. My husband put in a utility sink so we are able to do fast and painless water changes by just opening and closing valves and faucets. The python was a definite improvement from 5 gallon bucket water changes on the 55 gallon tank, but would be a nightmare, IMO, on the 300 gallon tank. Some people love tank maintenance and spend their weekends working on their tanks. Maintenance is not my thing. I love my cats, but I don't like scooping out their litter box...same thing with my fish...love my fish but don't like tank maintenance.