Is it more important to have a mind for God or a heart for God?
A balance is necessary for sure, but both are crucial.
I could probably make a case for each that would make it sound more important than the other, which sounds contradictory. This is because, in a sense, truth is the foundation of all right affections, while at the same time right affections (the heart in relation to God) is the goal of truth.
So you have to ask, Which is more important, the root or the fruit? If you don't have root you don't have fruit. And if you don't have fruit, then the root was pointless. So both of them have their own unique place.
One of the passions of my life is to help people be lovers of truth and lovers of people. If you don't have both then people-loving is going to suffer, and so is the truth.