They kinda go in order of sophistication and intent.
Cato's Hike is a goal oriented system focused on moving a character and thinking programmatically. It is all drag and drop, and I don't think it ncludes like numbers.
Scratch is a free-form system with good programming structure and ways to use math and such values to do animations and drawing.
Stencyl is a programming environment even more wide open than Scratch but based on the Scratch visual approach. It can be used to make applications and games for i devices.
So, that order would make a nice progression. One interesting thng about Cato's Hike is it was crated using Codea a full programming implementation of Python that is all text based and can make i apps. It is also a reusable skillset to learn Python to program other things like robotic systems or websites.
