I gave my nurse $600
In addition, we gave everyone company wide $125
Management and CEO get bigger ones.
Docs get nothing that would be considered a "holiday bonus," but at year end we give ourselves group stock options (if you deserve it), a tax distribution and an additional 1-2% 401K match (if there's extra cash to do it with + employees get too).
But it's 6 of one or a half dozen of the other. Decide what you're going to pay people for a year. If you want to lower the year round pay a fraction and give the difference in a cash "bonus" at year end, or a party, then it's up to you. Some people feel there's a little psychological boot and motivational persuasion by retaining a little extra and giving it as a "bonus," but it's semantics, if you think about it. But I also see the "entitlement" angle also, as once you start giving a year end bonus, you better plan on doing it every year, or you will erase any psychological boost you produced by giving it, the year you "take it away." I don't think these things make that much difference in retention, but they do a little. It's a combination of many factors, the overall work environment, and personal factors that also affect whether people stay or go.
Do what makes you feel right.