Horse of a half wagon

I don’t know why, but two colloquial phrases just never cement in my brain. Other people can say them just fine. But when I want to say one of them, the other one comes to mind and messes me up, and I cannot find the right word combination.

"a horse a piece" and
"six of one, half dozen of the other"

Both phrases mean that it doesn’t really matter. Same difference, if you will.

So, a few months back, in conversation with BJ, one of these phrases would have been perfect. I stumbled..."it’s a...six dozen...um...a...horse" and then frustrated blurted out, "it’s a HORSE OF A HALF WAGON!" He looked at me incredulously, eyebrows raised, as if to say, Excuse me? YOU are the English major and the journalist?

"Yeah, Ok," I said, "I don’t know, but you know...you know what I’m trying to say!"

In thinking about these two phrases, I realized that the "six of one" makes perfect sense. I get it. But the "horse" one? What the heck does that mean? A horse a piece? And then I wondered if I maybe knew the phrase's origin, if I'd be able to verbally execute it correctly in the future with confidence.

So, I did some research. Now, I realize the internet is not always the most trusted source, but I found in multiple places the same explanation for the origin of "a horse a piece." And interestingly one place said that "a horse a piece" is just the easier way to say "six of one half dozen of the other." (for some, maybe)

What I learned: the phrase "a horse a piece" originated in the Midwest where a common game played at the local bar was called "bar dice." If you were losing in this game, you were said to have "a horse on you." If everyone was a loser and had a horse on them, then it was "a horse a piece." Everyone sucked. Now, I couldn't find out why a horse. Why not another animal? Does it go all the way back to when people rode their horses to the bar and tied them up outside?

Well, whatever. I suppose it's a horse of a half wagon. Same difference. Ok?