Ask HN: Masters or Startup?

I have been working at a big company that does not challenge me for about 5 years. I have been meaning to make a change, now that the US is (sort of) coming out of the pandemic.

Two things happened recently: I found a cool startup that is interesting to me, and pays more than my current company, and I applied to grad school.

Assuming that I am accepted by both opportunities, I figure that I won't be able to do both. My current job is easy enough that I could take night classes and get a masters in a few years, but the startup is small, so I can't slack off with it at all. What sort of pros and cons are there for both paths? If you took one path, do you have any regrets?