You still have to pay attention to the memory usage of your game. So make sure whether loading a video in memory is more efficient then doing the "cut scene" within Construct 2 itself.
Depends also on the devices you target. Apple iphones don't like huge videos and you can't really navigate from a point to another within those videos.
Plus, as always with Apple, to start playing the video you are required to have a player input. possibly on a DOM object like a button.