The thicker the buttermilk, the drier or tougher the dough.
The thinner the buttermilk, the softer or stickier the dough.
The drier dough, tough dough works better because it holds its shape better, cuts easier and seems to cook faster.
The softer dough tends to want to flatten out, it's hard to cut, takes longer to knead, you have to add a little more flour to make it tougher. It also takes longer to bake.