There are problems associated with both tall buildings and low, spread out buildings.
A ranch is nice but you have to build a huge foundation to get a lot of square footage in the house. Invariably it becomes harder to keep piers level over a larger area. It is always a big investment to put in a full foundation, and a single story home means that the foundation will be a very large expense.
A two or three story house requires a really good foundation because of all the added weight, but it does not need to be nearly as large a foundation if the square footage on each floor is small. If you divide the square footage over two floors, you save about 40% on your foundation costs, clearing of the area etc.
On the other hand, the extra money spent might be worth it to you if you are older, and anticipate problems with climbing stairs.