Wow, where to begin... all good advice so far. The bigger the tank, yes, the easier to maintain, but also the more options for animals. Something else to consider is the size and spacing of saltwater animals. This is VERY different than freshwater. You won't fit as many animals into a saltwater environment as you will in freshwater, so getting a feel for the animals that appeal to you, THEN decideing on the tank size, will help a lot. Think about the triggerfishes... most of which will exceed 12 - 14 inches full grown and which grow quickly... waste levels are usually an issue due to space and feeding habits. Even domino damsels get 4 - 5 inches in diameter, while something like an ocellaris clown will top out at 4 - 5 inches, vs the tomato clown which can get 5 - 7 inches. Aggressive behavior is something else to consider, more aggressive fish need fewer fish in the tank, but much more space for territory, even if they are smaller. Even the clownfishes vary in aggressiveness.
The larger the tank, the more options available...
I have found saltwater to be less work than freshwater, but it requires a deeper understanding of the environment you are keeping. There are more water tests to do regularly in saltwater, but water exchanges can be a lot less, especially if the right equipment is there and it's set up properly from the start. There are sumps, canister filters, refugiums, IV sterilizers, and many other options for keeping saltwater, and they can be mixed/matched according to what you're keeping.
I always advise finding the fish you desire to keep FIRST, then consider what those fish will need, and work from there. It can be cheaper to start a 3 inche trigger in a 220 gallon tank and let it grow into the tank rather than starting with 55 gallons and stepping up in tank size every year.
There is one other issue I haven't seen mentioned, but I feel important to mention... size of the tank vs ease of having to do maintenance. The larger tanks are easiser to scrape and work in, but some may require a ladder for you to reach all the way into it. The stand on a larger tank allows more access for sump or other filtration options, and the use of skimmers and other equipment. Odd shaped tanks can be trickier to work in, and more diffucult to work with something like a sump.
Take your time, ask a lot of questions, take a lot of measurements, and have fun with it... this is a great hobby when you understand it!