Of the 6 or 7 men I dated in my life only one was my religion. He wound up being an ass.
My husband was raised Catholic, but his dad was raised Jewish. I’m Jewish. My husband did convert before we got married, but I never expected him to do such a thing. He wanted us to be the same, and neither of us are very religious.
I do think it’s easier if the two people are the same religion, but I think more importantly is the religiousity (I think that’s a made up word) of the people. If one wants to go to church every Sunday and raise their kids with lots of God and religious education, and the other is an atheist and thinks religion is all made up and a waste of time, that’s not going to work well. Or, if the husband is Jewish and won’t go to Christmas with the Inlaws, that’s not going to work well either.
Respect for each other’s beliefs is very important.
You really need to think about how you want your kids raised if you plan on having kids, and also realize many people grow and change when it comes to religion. Also, I think you have to be ok if your child goes the direction of the other parent even if you raise them in the other religion. Meaning if my Jewish kid decided he felt more comfortable with Catholicism I was ok with it. I’m not ok with some other religions and so I wouldn’t marry into them so fast. I still cannot ultimately control my adult children of course, but I can control some of the influences on them when they are little.