Impact and Construct are in separate categories...
Impact requires you to write everything in Javascript, but gives lots of template code and a good level editor. It is a great tool for what it does..which is HTML5 only.
Construct allows to write your game completely in Events with the option of using Javascript for plugins, etc..and it will have exporters to other platforms besides HTML5.
The type of user attracted to Construct (who doesn't want to write code) will probably not be interested in Impact...