Summer. Neither are very comfortable. In winter, you have to wear a bunch of restricting clothes to stay warm. In summer, your hot, but your not being bound up by your clothes.
Summer, but, I'm from the south, and we never really see winter here...but, I would take a hot, hot day over a below temp day anytime...summer is just like everything is new and bright and just I think makes you feel better....versus, winter, everyone seems more depressed and such, which both have their ups and downs, but, summer