In my opinion, just because your startup is valued at 100 million doesn't mean, your ownership will scale in a similar fashion. Many stories out there on how the founders screwed everyone or how the VC's screwed everyone.

To me when I had to switch to a startup, I did it for passion and I did it for the unique experience you get that you don't get at a big company. Also, you surely become more grateful to the experiences of the big companies, because you get to experience the chaos, the confusion (at times toxicity as well) and then be thankful for an orderly environment.

Agree with the part about not having regrets in part though.