You could easily grant employees "in the money" options that have a lower risk profile, and similar characteristics as RSU. This is effectively what an RSU is anyway, an option with a strike price of 0 that vests+exercises at some point in the future. Not to mention most startup options are granted at 409A valuation, which in most cases is below actual market value.
No meaningful difference between the two for the context being discussed above. Different tax treatment. Believe whatever you want though