Someone who believes something without evidence or someone who doesn’t believe something with mountains of evidence? Which is worse?

I would say the latter. As human beings, we tend to fill in the considerable gaps in our knowledge and experience with faith, conjecture, extrapolation or supposition all the time, and that’s usually ok. Choosing to reject evidence and empiricism tends to be far more problematic, since once we reject reality it can be hard to resist doing that all the time in service of our pre-existing beliefs, and that can lead people to do some really shitty things.