Im a freelance engineer, and all i can say is that there are two seasons. In one of these seasons you are working even on weekends, on the other season you are praying god to throw you a bone. And this happens even to the best of the best, the difference is how much these seasons last, some people have very short periods of unemployment, so its not a big deal.
I would say that being a freelance engineer lets you do a lot of things and lets you decide what to do and what not to do, it lets you earn more money per project, but you have to make sure you do enough projects, otherwise you are not earning as much as you think, even if that last project paid off very well.
Being an inhouse engineer has less "thrill" in a certain way that you are stuck with your job and your monthly salary, but at the same time you dont have to worry about not having a job.
However being a freelance engineer also prepares yourself to times of unemployment and gives you the opportunity to know more people, if you are an in house engineer and you are suddenly fired or "let go", you may find yourself in a position where you dont have a ****ing clue what to do next or who to ask for help... but if you are a freelance then its not that big deal.... (as long as you are not unemployed for too long....)
Although to be honest, being an audio engineer, regardless of the one you choose to be, is not easy, theres always a high risk involved, which is higher than say being a doctor, a doctor can open the newspaper and look for a new job, an audio engineer cant..... but overall its worth it, i guess....