> I've debated this with a couple of investors and their stance is if you leave the company then you're not committed enough and shouldn't receive anything. I think that's quite debatable

I don't think that's debatable at all; I think it's bullshit. Once your options vest, they are yours. They are compensation for the work you have already done, not the work you will do in the future.

Once/if your company switches to RSU grants from option grants, then at vest day your stock is yours, and can't be taken away when you leave the company (well, I imagine they could write up a contract that says that, but that would be quite non-standard, and I would never work for a company that did something like that). The vested RSUs are, again, compensation for the work you have already done, not the work you will do in the future. I don't see why options and RSUs should be considered differently here.

(I might even stretch that into the idea that it's bullshit that startup options expire at all, even if you stay with the company forever, but I do think that's debatable.)