I mostly use an M1 iPad Pro for personal use. I can get 90% of my personal work done on it, but not everything (e.g. I had to use my laptop for some tax filing work).
GitHub Codespaces works well enough to work on my blog but it’s not a replacement for the full dev environment I have on my laptop.
If you just had to pick one, I would go for the MacBook Air.
iPhone and iPad have replaced almost all of my personal computing needs. I still use a MacBook for a DAW to play guitar. I am traveling these days and the MacBook stayed home.
My work laptop is now an M1 MBP. It's working out fine (after a few Docker hiccups).