it depends on what you are looking for in a camp, and in my opinion, what age you are
i think windells is better for younger kids age 8-14 who want a really 'campy' atmosphere as you will be spending your time either on mountain or on campus where they have skate park, bike jumps, tramps and etc. you eat your food there, you sleep there, etc. its a really nice facility, but it's not like being in a whistler village where you have loads of options to choose from. i think it's an easier sell from the parents perspective because there is good supervision and its a really positive and encouraging atmosphere
at momentum (or coc for that matter), you are in the middle of whistler village and are given more liberties. i think its better for teenagers and adults who want to shred, but who also want to rock out at night and enjoy what whistler has to offer. you can go chill at the many lakes, go shred bike park in the evening, the skate park is sick, you can float rivers or whatever.