I would say that for most RSU lots it's better to wait for long-term capital gain taxes to kick in before selling.
(1) give you the amount in cash (as regular income)
(2) take that cash and buy that stock on your behalf
(3) turn around and give you the stock
and somehow you decide to let (2) and (3) happen without returning to the cash position in (1) and buying whatever else you would prefer to hold. The LTCG clock starts on that day, and all you're doing by holding your vested RSU is let someone else decide to buy stuff on your behalf and make the decision for you.(that's assuming that there's an ability to liquidate the RSU on the vest date)
The only reason to wait for LTCG on RSUs is if you decided to hold it for some non-zero amount of time after vesting and then the stock price shot up. But then you're also taking on the risk that the stock price will drop again before the year has passed, and end up with less post-tax money than if you'd sold at short-term tax rates.
Sometimes you can elect to sell every released share in a quarter, or file a 10b5-1 plan with a schedule, but you have to do that during a trading window.