If in a warm area, I would definitely go with two, because I like to leave windows open at night (and I like the idea that no one can stand outside my bedroom window). For everything else, a 1-story is better, but the two reasons I mentioned outweigh the benefits of a 1-story (for me). My biggest issue is the temperature difference between the two floors. With single zone heat/AC, it’s not possible to have both levels at a perfect temp at the same time. If you need a bedroom on the ground floor, they’re very easy to find, and I wouldn’t buy a 2-story without it.
I also like that my toddler gets practice on stairs, and it’s a very short period where they are still wobbly on the stairs AND can open the gate themselves.
