Well worth it. I've not been myself, but every one of my friends that I ski with have been there (makes sense, I ski at hood), and they progress so much. The parks are pretty similar, and I've heard the coaching is a lot better at mhssc aswell. The main difference is the offhill environment. mhssc still has a supertramp, skate ramps, and other activities, but it nowhere near the same as Windells in terms of options after riding.
I would say, go to windells for a good time and to progress in the park. OR, go to MHSSC and progress a ton in the park, and still have a good time off hill.