We wanted a large home so we built a tri-level on a fairly small lot. It's built into a hill, saving lots of $. Similar lots in our neighborhood have ranch homes or split level ranch, but we have twice the square footage - more room than we know what to do with in fact, and we haven't even finished the basement yet.
One disadvantage to a tri-level home is all the stairs, 3 sets of them, and hauling laundry and toys up and down and all around the house. Not a good choice for a final home either. I would want the bedrooms on the main level, or at least the master on the main level. You never know how easy all those stairs will be when you're older.
Good luck! Building a new home is so exciting.
By the way I've never heard the term rambler. What is it?