I've had the experience of knowing a lot of Scientist's and Engineers most of whom are secular because of where I work, and also Christians because where I live (and work).

I honestly can say most (over 99%) are nice, but i live in an area where greater 80% have technical or business college degrees so its not a random selection. Business people arent so nice though....lol!

Scientists typically 99.999...% nice by my experience. They go out of way to avoid conflict. Though there are wild exceptions.

I have met a more hostile Christians tbh, but they are usually conservative, and some are so horrible sometimes I don't even think of them as Christian, just someone who thinks they are.

My experience is that it makes no difference whatsoever.

I am an atheist, and I know some very religious people who are kinder than I am. At least that is my impression.

I have lived amongst Christians my whole life. Some are the nicest people you ever met. Some are assholes. I've only knowingly been around atheists about a decade and a half, and some of them are very nice and I've met a couple of Atheist assholes.
One thing I can't stand about most of the Christians I know is that they will believe anything you tell them, if it fits into their worldview. They will then spread it around their church and beyond. True or not. It makes me crazy that they don't care at all if it's true.

Well, speaking personally as one only truly can, Atheists, for the majority part, are somewhat kinder and more caring than the believers possibly because,
A) we are that way simply because we KNOW and understand that it IS the right, correct and decent way to be,
B) we do it because we can and we KNOW that there IS no Sky Daddy watching and taking notes,
C) we know that there are NO rewards awaiting us in some mythical, non-existent After-life, and best of all,
D) IF you're anything like me, you get a kind of warm feeling when you do something for someone in need of help, etc, EVEN if they don't actually thank you for it in so many words.

Non believers are definitely more generous than religious people, and also we are smarter. Studies prove both facts. [nydailynews.com]
[independent.co.uk]

I'm trying to answer this and cannot really. It's because I do not know. To me some atheists are stupid. These are the ones who cannot believe in gods but yet do believe in spirits and people on other planets, also thinking spacemen were our early "gods." The reason I call this stupid is because suddenly there are several things all at once to not have evidence for. This type of reasoning is why Scientology caught on with so many. You know, the religion started by an alcoholic science fiction writer.

Back to your original question. I'm not so sure I can answer it. I do believe that the kinder people are those who are not always making stuff up.

Being an atheist/agnostic does not make you better or worse than anyone else. So much is based on the individual and the circumstances.

I agree with what Ramona said about kindness not really being a reflection of ur religious views. But I find atheist to generally be as or more judgemental and condescending. And just for reference scroll through some posts here and see how many times u see fairy tales, stupid, close minded, simple minded, brainwashed, and indoctrinated mentioned to describe Christian's. And being offended by some that says bless your heart or merry christmas. And while I agree with some of those sentiments, I don't feel the need to go around constantly voicing said opinions. IMO if the phrase in god we trust, or merry christmas offend you, ur just as closed minded as Christian's ur judging. I know that's kinda different discussion, but feel they r closely related

Not necessarily but I can tell you some of meanest and coldest people I’ve ever met were in church and some of nicest in bars. It seems to me that non-Christians aren’t nearly as nosy and judgementsl

My experience is that many believers are more polite and respectful than the non believers I know by far.

Which one?