Since a decent Chromebook isn't much cheaper than a MacBook Air, I would rather buy the MBA if the Chromebook experience is unsatisfactory. I know that Linux and Mac OS are different. I have worked with both and for my use-cases, I can develop equally well on both of them.
I bought the https://frame.work Chromebook a few months ago, for a hardware refresh, but have been on this setup for 4 years now. If I need a real linux environment, I spin up a cloud vm as needed. The taller screen is actually nice and I hook it to two external monitors without issue.
If you’re looking for a cheap notebook to be able to do most dev on go for it. I just developed and deployed a Rails website this evening on my 100$ Chromebook. Everything just worked.
That being said, if you want to spend as much as an Air. You might as well get the Air.
I think Google gives you a choice to get a Chromebook as your main dev laptop, so it is capable, but anything you can do on a Chromebook you will be able to do on a Mac. If I had a choice between a Chromebook or a Windows computer I would choose chrome, unless it was a gaming pc, then I would then choose Linux.