It’s a great question, but it posits a false opposition. And it makes a key mistake about the nature of God.
First of all, yes, God IS big, and according to the book of Jeremiah (23:24), he fills heaven and earth. He’s everywhere all at once. He’s the God of the universe, in charge of and “interested” in everything. That, of course, includes the big things—world affairs, the economy, genocide, etc. Nothing is too big for him to understand, work with, or be touched by.
He’s also, and at the same time, concerned about individual people and can work in what we call the smallest parts of our lives—our schedules, our desires, our wants, our colds, our frustrations. Nothing is too small for him to understand, work with, or be touched by.
Jesus beautifully described the situation like this (Luke 12:6-7): “Are not five sparrows sold for two copper coins? And not one of them is forgotten before God. But the very hairs of your head are all numbered. Do not fear therefore; you are of more value than many sparrows.”
It’s just our limited understanding that leads to our thinking that God is only interested in part of his creation. We pattern him after us when we look at how pinched we are in terms of energy, concern, and concentration, and think that God is somehow like that. We have to prioritize in our lives, and we have to work to major on the majors. God doesn’t have that problem. He can do the planning, the strategy, the execution and the fine detail of everything—from creating galaxies to comforting a sad child to arranging a “chance” meeting.
He can not only handle all the big things and small things at the same time, he can care about them all too. We can’t do that, and we can barely wrap our minds around the idea of someone who could do that. But that doesn’t change the divine reality.