Audit firms may provide better pay than commercial when you are in senior / manager level. However, do bear in mind that the non-cash benefits from the audit firm are next to "nil". And what benefits they can offer are not particularly fantastic compared to some commercial companies. Also depends on your superiors and the firm's management.
Some people are more suited for the consulting line, some are not. Some need the non-cash benefits like full medical/hospitalisation, house/car loan subsidy, etc, some do not.
Personally, I joined the my firm 9 years ago with no plans to leave. But in the last 2 years of my time with the firm, I did not like the way things were run in the firm, and I got a much better offer, so I left. There is a saying "people don't quit their jobs, they quit their bosses". In my case, this is very true. I love what I do, but I hated the place and the people I had to work for. Whether this will be the same for you, time will tell.
As for working hours, I would say commercial has its ups and downs just like the firm. Depends a lot on the culture of the company you join.
consulting line?..u mean like go from the audit line to the consulting line (advisory) for a try out?...