An atheist's principles usually have to be deduced at the source, by e.g. talking to the atheist. This isn't hard, but it does take time. It usually doesn't scale to other atheists.

A moderately devout Christian's principles are likely ones you already know in some low resolution through cultural osmosis. This is reason enough to suspect that, ceteris paribus, people will prefer to engage in voluntary trade with the Christian over the atheist. It is less because of the Christianity itself, than because trying to follow a known standard for good conduct reduces transaction costs.

As someone who isn't particularly religious, but grew up in a religious household, and as someone married to a very religious person (different religions), I believe it's all about outlook.

Religion tends to give you several quite positive beliefs about the world that aren't entirely logical. Things like karma, the golden rule, belief in a plan, etc.

Generally speaking I also believe that religious people are more willing to trust and forgive. These are all pretty positive things.

And finally I believe religious people have a higher sense of duty to others, but the better term is probably responsibilism.