One of the great things about the Microbit is how simple it is - sometimes it is so much more difficult to produce something that is simple and intuitive, and that's the case here. The Pi Zero is a great device, of course, but as a full single-board computer it requires an SD card with OS, keyboard, display, etc. Now with all those add-ons it no longer costs 6 pounds, and neither is it as simple to use. With the Microbit, I've sat down with both young students and teachers and taught them how to use the block-style language to write a simple program and upload it in just a few minutes. They can then plug in a battery pack and walk away with it to show to their friends. It's a great board. Having Bluetooth on it is a ++, since you can then program it from a mobile phone. How great is that?
In the US it's been wonderful to watch the development of Adafruit's Circuit Playground, another really great board for learning. It has a slightly different intent, and it's programmed using the traditional Arduino framework, but having the Neopixels, speaker, microphone, and so many positions to attach clips for expansion etc is just brilliant. It's also super portable with a battery pack once you've flashed a program onto it.
Having all these options for learning computing gives educators, parents, and kids the ability to select what's right for them: the challenge now might just be getting the information out there so that it's easy for them to pick!