This one has been doing the rounds. I had one on Thursday and my parents who live in a different town had one on Saturday.
TBH it’s probably easier to just mail shot as you can A, cover so many more addresses, and B, are less likely to be abused at the door when you go knocking.
Although i have to say my last two experiences with JW led me to make complaints to the local Kingdom Hall.
First one I answered the door and they said that they were JW, no worries, not interested thank you. But after I closed the door they stood in my garden for about 5 minutes talking about what a shame it was, how I was obviously blind because of my lack of belief, and if only I would let them pray for me I could have been saved and would be able to see again. 
The second lot I opened the door and the bloke stood there almost stammering on the doorstep “er... uh.... er... we um... have... a blind person.” At this point they hadn’t identified themselves so I very abruptly asked them what the hell they wanted. It was only then that they said they were JW, at which point I pointed out that if they hadn’t been so incredibly patronising then I would have just said that no I just wasn’t interested, but given they had to speak like that in front of me before identifying themselves they could get the hell out and never come back.
On the whole I’m not rude to people, but there are always exceptions.
And before anyone suggests that maybe they just didn’t know how to react, I’m afraid that’s just not good enough. I can deal with people’s ignorance in the street, and usually it just passes over me and I laugh about it when I get home. But if you’re going to knock on people’s doors then you bloody well need to sort out your attitude, as you have no idea who is going to answer the door, and it’s their space not yours.