I don't know much about logic between two thermostats.
As already pointed out, a thermostat will only turn on or off at the set temperature selected.
Normally the highest area is the hottest area. So if it's colder downstairs, put the thermostat downstairs.
But us Brits have loads of thermostats throughout the house!
One for main hall/house temp, and the rest are all on radiator valves.
Every room can be individually temperature controlled..
But there are also these neat things that are wireless thermostats. You can have it in your back pocket and the temperature changes depending on your location within the property..
Even iphone apps too...Automation is now! Not the future.