You had to make me Google it!
Here is a cut and paste....
: Where did "A horse a piece?" come frome?
From various sites:
"This expression is used mainly in Wisconsin and the Upper Peninsula of Michigan. It means that neither of two alternatives is better or worse than the other. It's another way of saying "Six of one, half dozen of the other."
"Maybe from the Old West; maybe something to do with no matter how many horses you have, you can still ride only one at a time, so there's no sense arguing about how many horses you have available to ride."
It is a Wisconsin thing...like bubbler. Bubbler is a drinking fountain.
It's scary when you start making the same noises as your coffee maker.