If I really have to only pick between the two, then winter. With enough luck it can make people stay home instead of going to work/school. You can have a warm drink and cuddle a blåhaj without sweating a lot. You can protect yourself from the cold by adding layers (in summer you can't just tear off your own skin to cool down…). And with climate change happening, I'm starting to think I'm seeing the last of the snow to ever fall down here, so I would rather enjoy winter while I can. I do have some arguments for summer though, since I get hit by seasonal affective disorder, and going outside does improve my mood in general while winter encourages staying home.

I would rather pick autumn really. It's not too cold like in winter and it's not too hot like in summer, and whee it's orange everywhere!