Usually you get more options than you would RSU’s to compensate for this, but there’s still a risk/reward tradeoff. I have had stock options that ended up worth $0 because they were underwater. RSU’s would have been worth $non-zero.
The fact that RSU’s retain some value when the stock price goes down is highly relevant to a company like AirBNB which is undoubtedly struggling with the current situation. Also relevant may be that AirBNB isn’t a public company yet, making their shares relatively non-liquidifiable. This can pose problems both ways: if you get RSU’s in that situation you’ve received “taxable income” in the form of a non-liquidifiable asset and if you get options, you have to choose whether to buy stock in a travel accommodations company in the middle of a pandemic that just laid off 1/4 of their workforce, hence potentially incurring a very strong risk of loss.