Just a general advice. I was in same position few months back and i took more than a month to decide.
Before joining seed stage startups, you should verify that whether the existing team can take the startup 100X or not. 1% of 100M exit is nothing but 0.1% of 10B is big deal. You should have interviewed with atleast 5 startups before taking the decision. I interviewed at quite a few startups and i had multiple offers and i finally got the best deal i can ever get. I know that this startup founders are impressive and they are nice and they will do well. But you have to move out of your comfort zone and talk with 5 more startups. Then you will come to know about the startup market.
Please use wealth-front chart to find out whether you are getting right deal or not. https://www.wealthfront.com/tools/startup-salary-equity-comp....
Use www.Offerletter.io to validate that your decision is right or not. They have really great people who knows the startup market better than us. It doesn't cost you anything unless you get 20% more equity during negotiation. Of Course, you will get more than 20% if you negotiate in any company. Talking to them was worth it!
Don't join startups whose selling point is that they will get acquired as well.
Also, if you don't know what's Double Trigger Acceleration now, don't just join startup anytime soon. Read about startups and contact lawyers who are expert in stock options. They charge $300 but they save you $300K - $3M.
P.S: I'm not an expert. But I took more time to decide between offers and it gained me 2X stock options and 1.3X salary to me.
In very rare cases will you ever make a considerable amount of money when you take an equity deal as an employee. As we've seen from many buyouts, the VC get paid first and the employees usually get paid last after the owners.
I've had too many friends that got nothing after working months and even years at a job they hated hoping they would be able to cash out on their equity. I, myself, even got my equity liquidated to 0 after the CEO decided to completely dissolve the LLC and create a new one (A Silicon Valley trick talked about in the Social Network to push an undesirable partner out).
So, I would take the money every single time.
Obviously I don't have the specifics about you or this particular startup, but I can speak in general. A startup this early in the game has a 99% of being out of business in a few years, so you have to consider that. Let's take two scenarios...high salary and minimal options, say $150k and 500 options at $1 or you could go for high options and low salary, say 2000 options at $1 and $75k. Let's assume that if the company is not out of business in 4 years that it exits at a valuation 100x the current valuation. In that case, 500 options would be worth $50k, and 2000 options would be worth $200k. The guy who took the $150k salary would have made $600k in salary over 4 years, and would have a 1% chance that the options would be worth $50k. So the best case is $650k, worst case is $600k. The guy who took the options would have made $300k in salary, and a 1% chance of the options being worth $200k. The best case is $500k, but there is a 99% chance that he would get the worst case and just have the $300k of salary. In most cases it is better to just take the salary and a token amount of options. That said, there is the possibility that if the company is in the 1% that actually survives 4 years, that there is an even more remote possibility that they may go on to be a unicorn type company and make secretaries rich from options. In that case, even a token amount of options should make you fabulously wealthy.
Take the salary, and renegotiate options on raises/promotions at a later date.
Any non-controlling non-preferred equity in a privately held company is worth only what the controlling interests give it via good-will. Controlling interests can always liquidate a company to themselves for a nominal price or award themselves preferred stock or pay themselves absurdly inflated salaries or rent office furniture from themselves or their spouses or anything else that allows them to move money from one pocket to the other while taking a cut on the transaction. And that's before you get to Private Equity/Venture Capital whose business consists largely of extracting as much value from a company for themselves as is possible.
That's not to say everyone is ruthlessly sociopathic. But only that the odds of turning equity into cash are lower than the odds of a startup having a successful exit and to suggest that it is quite possible for people to optimize their slice of the pie when the pie is filled with serious money.
Finally, on a $4 billion exit 0.7% versus 1% versus 2% isn't going to have a dramatic effect on your lifestyle. Same is true at $40 million.
Good luck.