As far as I could gather, cocoon (by that I mean canvas+ for android (?) and webview+ for iOS8) gives the best resukts performances wise, but (canvas+) can be a bother sometimes due to compatibility with C2 issues.
Crosswalk is chrome for android, it just is, while it is also possible to use cordova plugins for a lower level control of the device, it is not a really powerful solution as far as perfs goes, and it adds a fixed size for every single project, even the tinyest one (basically adds the chromium engine on top of your game) however as far as I know it is completely free.
Cordova (and phonegap) is basically having your game run in the device webview (although in iOS I heard issues were presents, you will have to search about that), jnder android lollipop, it is not good enough, under iOS8, it is not good enough, however there are quite a lot of plugins to add functionnalities.
Ejecta, I am not sure it works with C2 anymore, I though it did not but I could be wrong, I still think it was not as good as webview+ on iOS8.
I talk as someone who does not use any of those solutions (actually I kind of think wrapping a C2 game in those is stupid and using C2 only to go to the web export is the way to go, but that's just me), so the informations may not be up to date.
All of those solutions can be used with in game advertisements, even though I don't know how or if there are issues.