Warm it was 37 degrees celcius today and I loved it! When it's warm you can go cycling, running, swimming, sit outside and read, do not have to wear a ton of clothes. I am also one of those people who are almost always cold and I hate it. Furthermore when it's cold I tend to suffer from SAD. Not cool and not fun. So heat all the way for me.
In what situation? If you're asking if we would simply rather be cold or warm, then I have to say "warm", as I don't think too many people in the world enjoy being cold.
However, if you're asking if we would prefer a cold climate to a hot one, I have to say cold. Give me my snow with a warm blanket and hot chocolate any day.
I'm a man who loves the cold... There aren't too many circumstances where I seek warmth as I am usually pretty warm right around the clock. I guess I would prefer warmth over coldness in relationships though :P.