gdog105 If ReVeN uses WebGL then it won't work on WiiU for now, as it currently only supports HTML5 Canvas 2D (no WebGL FX, performance boosts, etc). That said, they might not use any WebGL, so then it should export no problem (not sure about performance though).
Most Construct 2 games that get a WiiU port and are fairly large seem to be porting to Unity to reach consoles (which also allows the export to PlayStation, Xbox, and someday Nintendo 3DS, etc).
As for what is more powerful between WebGL and Flash, I would say WebGL seems to be very capable of matching the best performances Flash can get, and in some cases surpass it. It really depends on the engine, how well the game is developed performance-wise, and the machine you play on (PC, phone, console, etc).
Hope that helps