The bigger the tank the easier it is to keep parameters level since you are dealing with more water volume. You still have to do water changes and maintain it the same as you would the smaller tank but if something goes out of whack theres a better chance in a bigger tank of catching it and fixing it.
Petco might still have their $1 a gallon sale going on, so $55 for a 55 is a great deal. But if you have the room and money a 75 would be even better suited. You get an extra 6 inches from front to back which gives you soo much more room for rock, coral and fish. Both the 55 and the 75 are the same length, 4 feet. The only difference I believe is that 18" from front to back.
The column tank I had didn't work out too well for me with freshwater even, I ended up giving it to a friend. I knew within 2 weeks that it wasnt gonna cut it. lol I went to a 55g from that with FW
My first sw
tank was a 29g which worked really well for a couple months until I needed more room for corals and fish. Then I went to a 55g which was a nice upgrade but if I had to do it again I would have just started with a 75. That extra 6 inches is a god send! LOL
Good luck in deciding, let us know what you end up doing.