If you're expansionist catholic nation, narrowminded let's you get cardinal spots, which increases your infamy reduction.
It also let's you become the papal controller, which let's you cancel RM without stab penalty. Great for abusing Claim Throne mechanic.
Well, I am definitely trying to expand. And since all of this is before the reformation, (well before, around 1450), I'm Catholic too. I have actually decided not to go around claiming thrones this game, so that last part won't help. But I had no clue, so that's awesome. Being able to get rid of marriages without stab cost is cool
The main benefit to narrowminded is the bonus to stability. That's more useful for larger countries, except that larger countries have even more tech problems. Basically, in my experience, smaller countries don't need the stability boost, and larger countries can't afford the tech penalty.
Well, as of right now, I control all of the Netherlands, Oldenburg, Bremen, Namur, Ghent, Aachen, and 5 coastal provinces from Mutapa. I have the colonies Azores, Canaries, Cape Verde, Madeira, Eiriksfjord. In a few years, I'll incorporate Munster (mission). So far, it all balances out well because I am the sole western nation to have trading access to Kutch and Malacca. I tech hard, although not epic. But the colony growth bonus seems nice as well...