Which means the employee has to realize income tax on the stock immediately under an 81-b or after vesting, correct? That would be an annoying and surprising tax bill, if the employees are mostly familiar with ISOs or NSOs.
http://www.investopedia.com/articles/tax/09/restricted-stock...
With RSU you can't opt for 83-b and you only pay tax when vested. I am just an entrepreneur not o Tax advisor :)
for readers that don't know what a RSU is
http://www.calstartuplawfirm.com/business-lawyer-blog/restri...
In a nutshell I think the main diference of RSUs is they compensate based on the full value of the stock, whereas NSOs (Nonqualified Stock Options) only compensate on the stock's appreciation in value.