Depends on my free time, honestly.

I enjoy world building, and I think its incredibly satisfying to open up something I've created so that other people can come in, participate, and expand on it. But life often gets the better of me, so when the going gets hectic, I'm more content to play in someone else's sandbox.

Long story short, I guess, I'll GM when I have the time. Otherwise, I'm just happy to participate.