This is a little late in the subject, but a 220 is pointless to spend the extra money when a 180 will do the same job. The extra 6" of height is pretty much a waste with a shark tank. The foot print is the big issue.
Tank, this hobby is expensive! Stuff adds up quick and you don't even know it. When you get into big tanks and with sharks, it goes up exponentially!!! Think of the skimmer you'd have to have on a tank that size, not to mention all the plumbing, water movement, heating, electric bill running it all, it's insane! Good luck with your setup, just take your time and think things through, don't want to see you make mistakes and get discouraged and get out of the hobby. Maybe you should start with a small FOWLR tank just to get the hang of everything before attempting a shark, they are a lot pickier about water quality etc then most fish.