You pay taxes when RSUs vest. You pay taxes on options only when you exercise them. In addition, when the RSUs vest, they are yours when you leave the company,

You pay taxes when RSUs vest. You pay taxes on options only when you exercise them. In addition, when the RSUs vest, they are yours when you leave the company, with options you have to exercise within a time period (a short one if it's an ISO, potentially 10 years for NSOs).