Difference leaving big 4 as a senior vs manager

Background - tax senior investment management group at pwc. just finished my first year as a senior. Total I have 3.5 year at pwc. Thinking about going to private client or admin firm. Salary pretty much is the primary factor if not only one I care about. Should I stay for another 2 years to go for a manager and leave? Or should I leave right now for private? My concern - heard that it is hard to get promoted at private firm and annual salary raise sucks. True or false?