Our master is on the second floor but none of the walls touch another bedrooms. The suite is the back of the house and kids bedrooms are in the front. I love this design because I have a 1 yr. old and a newborn so being close to them was important. But I still wanted a feeling of separation. I could have done first floor master but it would have cost more and resale around here would not bring me a definite return. I was able to have a much larger suite putting the master on the second and get my dream bath. We have a large bedroom 17x 13.6 on the first with a modest closet and shower bath. It will either act as a guest room or an office for me.

I would say to do the same if you aren't sure or if resale will be iffy.

Having a large ensuite room on two floors can work really well if they are able to be multi-purpose. The large downstairs one can serve as an office/guest room/media room if the upper is the designated master. And the upstairs one can serve as a large playroom/teen study/guest suite if you prefer to occupy the downstairs room as the master. This generally works out best design wise if the upstairs master is over a garage area, but only if you take the time to properly insulate it. Most "bonus rooms" above garages are poorly done in that regard and remain uncomfortable spaces as a result.