The Christmas Day thing is a bit of a 'tactic' as they know people will be home. It's also a good way to get the attention of anyone who's not enjoying the festivities by presenting them with reasons why you're not supposed to enjoy it. And people who are lonely.
They are just the same as any group of individuals, some are lovely and kind,(especially the women ime) some aren't quite so lovely but make it their business to seem so, and some of them are awful and arrogant but put on a good show anyway.
All of them are easily persuaded by not very convincing 'literature'.
I actually have the impression a majority of them aren't that keen on the door-stepping themselves, but they are, if not forced exactly, then heavily pressured into doing it. They often just want to place their mag so their numbers look good at the end of the month, without meeting with too much aggression, and back to base for tea and cake.
Every one I've ever met likes a drink.
If they place a mag then they will write you down as being potentially interested but it's really less to do with hassling you and more to do with being able to show they are making progress and have some ongoing 'goals' in their evangelism.
They are unlikely to be anything but pleasant if you tell them no thank you. If you look up your local Kingdom Hall and ring them you can be added to the no call list.