Definitiely Linux (except if you're doing iOS/macOS or Windows development of course).
macOS software declined in the last years so much that i switched to linux myself just a few months ago and i couldn't be happier.
if you already have a mac you can try to run linux on it but basic rule of thumb is: if it has a retina display, forget it. it kind of works sometimes but you will get frustrated and hate it. sell it, get a thinkpad or dell xps.
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