I've gotten several questions recently around when to use App Lab vs when to use Game Lab. The linked pages provide demos, videos, and sample projects, but I think it's still an interesting discussion.
I like to use Game Lab whenever I have an idea with a lot of movement or drawing because the animation tab and draw loops make this very customizable.
Here's a project I made called "Bugs and Flowers"
I use App Lab when I have an idea that requires me to switch between screens or collect data that I need to store.
One example is "Choose your own adventure", which is from code.org/applab
What scenarios do you use these tools for? Feel free to share your sample projects.