You have to stay for the liquidation event, right? Even if you have a large amount positive there you're forced to remain at the job until the liquidity event.
- At year 0, you're granted 100 RSUs on a double trigger with a 1 yr cliff, monthly vest after
- At year 1, you have vested 0 but if the company went public you will immediately vest 25
- At year 4, with the company still private, you have vested 0 but if the company went public or had a liquidity event you will immediately vest 100
- At year 5, with the company still private, you are going to quit. If you vest now, you must pay tax, but no way to do that with cash unless company withholds RSU percentage
In the double trigger case, at year 5, you leave empty handed. In the single trigger, you pay tax with illiquid stock (through withhold or pay cash).
I've always only had options or stock, so do correct me if I'm wrong.