Stencyl is not flash anymore but hex. So native export capabilities on multiplatform.
It has a decent fps and decent performance. And imo better design.
The con is the price and less community.
The pro is that you can actually build ios game without third party wrappers. I think it's the downside of scirra.
If you add multiplatform support (mac), real multiplatform export ( i know js is very bad to translate in native code).
C2 can even actually call itself C3 and will be the best engine ever.