A feature is a relationship with god. A Benefit is eternal life.
How do I have a relationship with something I can't see, understand and is probably me talking to myself? I have a great relationship with my dog, better one with my wife, teenage daughter, well she's in those difficult years.

As for eternal life which is a benefit. Who do I talk to who has this benefit?
Benefit of joining a church are, a superior feeling one understands something others don't. Belonging to a club so social benefits of like minded people, having somewhere to go on a Sunday morning.
The downsides are. Thinking one's a sinner, getting a feeling of guilt when looking at a beautiful woman, having sex for the sake of pleasure, being a woman, being conceived and born, not being good enough to make the grade of Heaven, giving money to a church. Over the years there have been more. Many we have dropped, even though they're written in the bible.