The so called promotion/progressions are just titles artificially created to show there are progression but in actual fact it is the same position. I.e senior and managers are 3 years each. You dont tell people you are M3, only audit managers.

The higher increments are due to the audit firms squeezing/frontloading alot more working hours into a work year.

I.e You can get $500 increment in a year because you worked 10,000 hours in one year. You might also get $500 increment in commercial if you worked 10,000 hours just that you might take 2 years to clock the same hours.

So ultimately it depends on whether you treasure work life balance and starting a family. Big 4 is losing out now because there are new industries and positions opening up that can offer the same compensation with less punishing hours. Basically it is a sunset industry.