While both are beautiful, I'd have to say I like summer in Narnia better; they've just seen too much snow enough to last a lifetime. The summer would remind me of Aslan being there again and of the White Witch's power gone.
I love Narnia in the summer. I really don't like snow that much. Over my 60 year life span, I've had to shovel too much of it, get stuck in traffic because of it, go sliding in my car on it, and freeze my butt off in it. Give me sunshine and warm temps anyday.