If we are talking a summer tour with some 30 F nights when at altitude and some 100+ F days in the desert, then heat is more likely to bother me.

If we are talking about actual winter touring in really cold weather, then I'll be either XC skiing, trail running, snowshoeing, backpacking, or at home. If I am on a bike at all in the winter when it is really cold it is likely to be a mountain bike and off road. In any case I prefer not to tour when it is consistently really cold. I can take a bit of cold on a long tour while at altitude. I will also tolerate some 100+ heat, but I try to minimize my exposure to either when possible.

On both the Trans America and the Sierra Cascades we had some of both. The cold tended to be tolerable mostly because it was for brief periods in specific places. The heat was worse because sometimes it was well over 100 F for longish periods.

BTW, I love sub freezing winter weather for snowshoeing, trail running etc. I am just not crazy about riding in it.