I dig up this topic just to say, I hesitate a lot between Stencyl and C2.
For sure C2 is easier to use, while Stencyl is a bit more complex. Stencyl uses Haxe and can compile natively on several platforms.
The fact is that to go on mobile, or in FGL or on Armor Games, Flash still the best option in this start of 2014.
I have a few apps done with AS3 or Haxe on my old iPhone 3GS than run smoothly than HTML5 games actually.
In the browser on PC, HTML5 could be better (becoz of WebGL better support).
Anyway, I'm not sure it is worth trying to tell wich one do better, as it's a matter of choice and personnal preference. And quality of work When you go to big projects, it could be a big mess anyway.
Look at games like "Papers please" coded in Haxe (OpenFL ex-NME) or CoinOp story coded with C2, the two are very well done.
For now, the ease of C2 and the nice preview in browser make it a very good start, at least for beginners.