COC has the best summer park and a chill environment. The place is huge, and when you get back to the village you do what you want. You don't have to be anywhere at any time.....Freedom. Go there.
The Public Park in Whistler isn't that good, but the Windlip is badass. If you're 19 or over I would just go to Whistler and shred public park and party. If you're not, go to Hood and rip their park... and not park.