I left as a senior tax to private and although obviously it depends on where you go, it has a two fold answer.
If you want a more stable work-life sooner rather than later, its a good choice to leave after senior. However, moving up industry is much harder in private especially if you have a manager that doesn't intend on leaving. In public, a senior can get promoted (of course with a CPA and good track record) after 2-3 years. Also note that a “senior” in public is practically a staff unless you have paraprofessionals helping you out or temps helping out during tax season that you can “senior”. Managers are typically the “seniors” since they are 1 level up….but it depends since it could be more parallel to a Big4 if its a big tax department. Being “stuck” can be the first feeling you will get if you leave however it varies by the type of place you go since if theres a clear path for you to get promoted, then there's no reason to stay in Big4 esp if you don't foresee yourself going farther/dealing with the Big4 demands. You also have to think about the flatter raise in private industry. Big4 actually offers higher raises, at least in my experience.
If you want a higher pay base/bigger payoff, staying till manager has its perks. I didn't choose this route since I wanted more family time flexibility quicker but almost everyone I know did and it worked out well for them. You can jump as a manager but then again you have to deal with 2-3 more years of “big4”.
I left as a seasoned senior to be part of a tax department and although there's no prospects anytime soon of being manager, the work has been rewarding. However, you just have to be true to yourself that making manager at Big4 isn't a big deal because if it is, it will eat you alive once you leave. IF you can get past that part, private industry can offer plenty of doors. Then again, a person with enough Big4 senior experience + private industry experience = can go get a manager gig elsewhere.
Hope this helps.
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