[badcppdev]

My 2p as parent with RPis + multiple Microbits in the house.

Microbits are far more limited in their capabilities but they are a useful stepping stone because they are limited. They can be used like a piece of lego as part of a larger creation.

They have inbuilt switches and sensors and it is easier to connect extra components to a Microbit. You don't even need a breakout board. They run off batteries quite happily and once you have uploaded a program onto the Microbit you might only need that single battery box. And if you have two or more of them then you can use the inbuilt wireless connectivity very easily.

The proprietary nature of the code running the RPis and Microbits is not a factor for me. Once my kids get closer to being teenagers hopefully there'll be some fully open platforms available for the next steps.