[olliej]

It would depend on workload. On my old intel MacBook, I was looking at an hour or so to build, and it could only complete one build on the battery if that. Testing took a similarly absurd amount of time.

The M1 dropped both times by in the region of 30 minutes, could do multiple rounds on a single charge and didn't make a tonne of noise while doing so.

The amount of time savings you get from the improved CPU perf is quantifiable, and you can assign a monetary amount to that time.

Now if your use case is not performance (cpu, battery, etc) limited then of course there's no reason to upgrade, ever really, but that would apply to any laptop or pc not just Macs.