You get all of the cons of running your own business (stressful, wearing many hats, little compensation up-front), none of the overall control, and if it's ridiculously successful, your compensation will most likely be squeezed out during one of the rounds of investment.

Wearing many hats isn't always a con, my first job as a software engineer was at a startup and I couldn't think of a better growth experience because of that very aspect.

I'd also argue that you have more control as literally any employee of a startup because of looser power structures, proximity to upper leadership and generally more transparency. However how controlling your shareholders are will be situational.

Likewise getting squeezed out of compensation very much depends on your situation and status at the company. If you're a cofounder you'll probably be alright, if you're within the first ~10 employees you'll probably be alright, after that you'll probably still get a nice chunk of change. Though maybe not enough to make up for smaller up front compensation but that also was not my experience (outside of the bay area).

On the first point though I'll admit that it's not better for everyone. We had hired a GPU & camera driver expert and had him doing odd jobs on our Android app for well over a year, but that was more of a problem with hiring and then with management after he was hired.