I'd say Canon and Scratch are different tools with different purposes. Both are simple and interactive enough for children to love. The main difference I see is that Canon abstracts away a lot of the game state management logic and you get to focus on creating characters, items and having lots of fun. Scratch looks like it has a steeper learning curve and while it is a good introduction to programming, it gets pretty hard to navigate once project size increases. As someone who started programming with Scratch, I think that making a text adventure game like the ones Canon does in Scratch would be much more complicated and the end result wouldn't be half as nice.