It's a bit like picking an office chair.
You can read tons of books about what makes a great office chair, you can read reviews and all.. but to pick one you have to sit your ass down in it. Because the reviewer might have had one bony, skinny butt whereas your behind resembles that of an elephant or vice versa
The C2 community is active, the devs are active (regarding updates, forum posts and pushing the boundaries of the tech), overall it's buzzing like a beehive.
But it won't help you if you don't need a HTML5 engine but something else. Insofar Stencyl and C2 are not really comparable.
So take advantage of the free edition and test it mercilessly.