The holiday is more of a backdrop to the usual goings on in the hospital. It's all the same drama, but with a Christmas tree in the background of a scene. If anything, the holiday is used to occasionally show the passage of time, but in 16 seasons there have only been seven episodes decided to the holiday. (Dedicated is a strong word considering that some episodes have given less than 10 minutes of screen time to the event.)
There are some Grey's Christmas episodes that are more happy than others and that feature the holiday more prominently. If you're trying to decide which of the episodes you should watch this holiday season, here are all of your options ranked from least cheerful to most.