It depends how religious the girl herself is. I think one of the positives of religion is that it encourages self-control in people especially when it comes to promiscuity, so dating a girl from a religious household can be a benefit in this regard for someone wanting a long term and monogamous relationship.
So, provided the girl isn’t wanting to engage in hours of religious ritual daily, I see no reason it’s not a positive. Religious people also tend to be more in communities and it seems nice to be joining a community, part of the whole appeal of a relationship to me is to be able to join the family and community of my gf, meaning I’d have more friends and support in my life (and of course to give back to them as well).