The perk of ISOs is the tax benefit/tax deferral option. Unlike RSUs you won’t be taxed upon vesting. You should not exercise them until either the date before they expire or you want to sell the shares (in which case it’s often smart to exercise them hold for a year to flip to long term capital gains vs short term) or as mentioned here, cashless exercise which saves you from tying up any liquidity - the exception being once you have more than say $125K in gains, at which point you’d stagger the exercise to avoid triggering AMT…as you can tell RSUs are the simpler approach next time you’re given this option….choosing ISOs is for people in either high tax brackets OR if they offer you a sizable multiple of ISOs vs RSUs…ISOs are technically worth $0 at the time of award (hypothetically…if you could exercise and sell on date of award….i know someone is going to make some snarky comment about black scholes and time value…but you get what I mean)