My experience is probably not relevant to the audience here, but having worked at startups largely in non-engineering support roles that got smaller or heavily diluted grants, I've lost about $3,000 on options in 10 years in tech.
I paid in $17,500 at two places where I had vested any options, all ISOs, and cashed out ~$14,500: broke even on an IPO at $7,500 vested, and lost $3k of $10k after the company was sold for less per share than the strike price of my options.
If I had stayed at the IPO'd company longer I could've gotten a higher-class of option, but my salary there was $15k/year less than the bootstrapped no-equity company I left them for, and the returns over two years of vesting would've still been less than one year of difference in salary.
At most of the places I worked, I either didn't make enough money or experienced too much external financial distress to actually buy all of the options I vested. Which is good, because none of them appreciated and most depreciated in value by 20%. If I had exercised all of my vested options I would've lost up to another $5-7k - at best I would have lost another $2-3k.
The only RSUs I was ever offered vested 2 weeks after I left a job that I'd had for almost six years, for a role elsewhere paying $25k/year more. The RSUs were a surprise bonus worth less than $5,000 and tacked onto everyone at the company, including roles that had already gotten larger RSU grants. If I had stayed two weeks longer and vested them, then when the company sold they would've been worth less than $4,000. Between the salary difference, a much smaller insurance deductible at the new job, and a 4x larger 401k match, I had effectively made up the difference by my fourth paycheck (eight weeks) just on salary.
On my experience I'd take the cash every single time. Reading the replies here, it seems like engineers, managers, and early hires live in a completely different reality regarding equity.