well, looking into the running cost between a marine tank and fresh water tank as well if that plays a factor in your decision making.
personally I like a well aquascaped freshwater tank better than a marine tank but that's just me.
once you move into the new place, figure out what's the biggest tank you can get into the house to where it will be setup, then hunt down the tank first. once you have the tank there you can take your time to figure out what to keep in it.