7 sharps or 5 flats?

I often find myself trying to remember all the facts I learned in undergrad about music theory.

And I found myself pondering in the middle of the night just why a piece would be composed in say, C-sharp versus D-flat.

Not that when you play it there's a difference. (or is there?)

But for me, I always found it easier to read music when there were flats, not sharps. Why is that? In fact, one of my favorite key signatures to play in has always been G-flat (NOT F-sharp). Hmmm.

So I'm sitting here struggling to figure out why a composer would prefer sharps over flats ... is it just a preference? Is there a tonal difference?

Anyone?