My 2 cents - it's harder to deliver the news in person. Been there done that. If you go the phone route - I honestly find it helpful to have my talking points with me when I'm on the phone and give myself a pep-talk before conversing (seriously!).
You do what is right for you, but again my vote would be to do it sooner rather than later. And it could be easier on the phone. Less time for manipulation and you can enjoy your holidays and new year that much sooner
