That was my whole thing when we looked for a new home. Both of us can manage stairs just fine, but I have a back that goes out from time to time, plus you never know what's in store when old age comes around.
I would go with a master bedroom downstairs, just because I'm hoping the next house we buy is the last house we have to purchase and a master bedroom downstairs seems to make more sense to me as my husband and I get older No stairs for me to fall down at 70, thanks.
I prefer a master downstairs. Our master is up with all the other bedrooms. When we go to build a house it will be a one floor plan with a basement for rec room etc. I will never live in a two story again. The exercise is good, but so inconvenient. I might mention we only have one bath and it is DOWN, so after shower, back up to get clothes. Oops. forgot socks, back up to get those. Oops. Forgot this, forgot that...a big pain when you're in a hurry and I'm NOT a morning person!
It depends on how old you are and how long you think you will live in your house. We are in our forties. We bought our house two years ago. Our master suite is upstairs, but we have a room that could be easily be made into a downstairs bedroom. We are looking for a ranch right now- not because we need it now but feel we will probably want it in about 15 years.
We have a one-story house, but our dream house (which may never be built, but we have house plans for) has a master bedroom downstairs. We thought it was best for several reasons:
1. Privacy for us.
2. Privacy for teenagers upstairs.
3. No stairs to worry about when we're old and feeble! We can just shut off the upstairs when the kids are grown and moved away.
Our master bed/bath and office/library are all upstairs and I love it! When guests come over they've got the run of the entire first floor, but the upstairs is our private sanctuary. Plus, we have a great view and being upstairs enhances it.
There is a large bedroom and of course a bathroom downstairs so someday in the future that can become the master bedroom and the upstairs could just be unused.
Happycat, for the reasons you gave, I used to love having an upstairs. My ankles hurt so bad that stairs are hard for me now. Another nice thing about having an upstairs is airflow. With a one level house, you don't get that. I love having the upstairs windows up at night in the warm weather and not worry about anyone breaking in when you have an upstairs. Also, on a warm day the air coming in the windows upstairs drifts down the stairs and cools the downstairs too. Even when there doesn't appear to be any air moving into the downstairs windows, this seems to happen. The feel of a two story house is different too. It has a grander feel, whereas my house now is kind of boxy. I live in a ranch house now, with a partially finished basement and I really miss my two story house. Physically, I'm not sure if I could do a two story house again and of course, with a two story house, you have to have a planned fire escape plan.