geekbench scores are roughly double for the m6 over the M1 Pro single core and multi-core CPU

https://nanoreview.net/en/cpu-compare/apple-m6-12-core-vs-ap...

In terms of performance, the difference is active cooling. That will matter to people who are regularly doing sustained CPU or GPU intensive workloads.

The Pro has a bigger brighter ProMotion display. It has active cooling, larger speakers, more ports, longer battery life, better graphics performance, better keyboard, and a larger default storage option (starts at 1tb).

If the Base M6 is good enough processor for you but want a more "premium" product, then the base Pro makes sense.

Better display, more ports.

Also, there is no M6 Air yet.

I got an M5 Macbook Pro instead of an M5 Air because the Pro has more screen real estate, a much better screen, and its fans means I never hit the thermal maximum of the laptop.