Cash is king, startups will want you to feel "family" but you'll never be one. In the unlikely event equity is worth anything, converting it to cold hard cash is not always straight forward. In other words - take the money.
People rarely seem to understand this. A successful exit doesn't necessarily mean employees will get paid. A friend experienced this when Google bought the start-up he had been at for 2 years. Employees had to wait a year for an earn-out period. They had to re-interview for their positions, and fired if they didn't meet Google's impossibly high standards.
(edited to clean-up a grammatical error)
So he took 2% options at a 50% pay cut, but then got fired and that screwed him out of the 2% options before he could vest.
Welcome to the valley.
If they were children, why were they running a company? Why would anyone join a company run by children?
Edit to add: That link describes in fairly precise detail the nature of the person's death. If you think that isn't something you want to read, give it a miss.
I'm old and jaded, but salary should be your primary metric. Stock options are worthless. I took a 50% cut at PagerDuty (YC10) for 2% of the stock options, they're now worth $1bn+ and screwed me pretty hard, the day after my father died. They didn't even offer any severance pay until I pointed out how much damage I could do to their reputation, then they gave me a week. Start-ups, especially run by new founders, don't know how to treat people humanely. Thanks guys. Since then my attitude is, "Fuck you, pay me". You will not win the start-up lottery. If they don't offer an 83(b) election, you could end up in the red if they do exist. This happened frequently in 2001, it even lead to several infamous suicides.[1]
Are you 200% sure you will last the 3/6 month signing-bonus waiting period? If not you could end up with a liability greater than the value of the bonus. I had this when when a start-up outsourced ops to LoudCloud. They contested our unemployment claim and I spent $3k in legal fees fighting them, in the middle of the start-up recession.
Start-ups will not invest in you as an employee, and will drop you without a second thought. Expect to spend all of your free time learning new skills just so you don't get fired.
[1] https://www.siliconinvestor.com/readmsg.aspx?msgid=17123680
(edited for spacing, and to add the anecdote about severance pay)