I find Marimo best for when you're trying to build something "app-like"; an interactive tool to perform a specific task. I find Jupyter lab more appropriate for random experimentation and exploration, and documenting your learnings. Each absolutely has it's place in the toolbox, and does it's thing well, but for me at least, there's not much overlap between the two other than the cell-based notebook-like similarity. That similarity works well for me when migrating from exploration mode to app design mode. The familiar interface makes it easy for me to take ideas from Jupyter into Marimo to build out a proper application.