You may recall from grammar school that we humans are warm-blooded, which means that we do not depend on our outside environment to regulate our core body temperature. Meanwhile, how many people have you heard announce they were "cold-blooded"? Not possible, right? While cold-blooded is not accurate in a technical sense, it is practically true regarding our sleep environments.
None like it hot
Human temperature normally ranges between 96.8 and 100.4 degrees Fahrenheit. Variation within that can feel significant. An important part of our circadian pattern is the movement from highest temperature (late in the afternoon) to lowest temperature (early in the morning). The dip cues us to sleep and sleep well. The temperature of our room can make this easy or difficult for us.
Optimal sleeping temperatures are between 60 and 67 degrees Fahrenheit. Anything above 75 is problematic and dipping into the 50s also seems unnecessary (and impossible unless you have a meat locker). No one really likes a hot sleeping environment--even if you fall asleep your amount of slow-wave sleep is reduced and you wake up more often. If you have insomnia or other sleep conditions, heat is bad for them.
Men vs. Women
This is not license for whoever prefers the colder temperature to reign over the thermostat. Usually the fellows do maintain a higher internal temperature because of higher muscle mass and metabolic rates. But exercise, diet choices, and individual differences can affect who feels comfortable at what temperature
One Solution is to stay in the same bed, but to use different blankets. Often when one person is on top of covers, the other can feel constricted. This method works best in a king-sized bed.
A less romantic solution is to retreat to a guest room and close the vents if you are the warm party. Maybe this is just an occasional measure when one of you binged on carbs or worked out harder than usual.
Serta among other manufacturers carried at Bedzzz Express are using materials that release heat from mattresses as well as actively cooling beds. If you don't like the option of keeping your a/c running constantly, keeping the bed itself cool is another answer for your cold-blooded sleeping partner.