The first instance where it occurs is when a MC is discussing the fact that she needs bullets and/or has other particular limitations in a fight but on the other hand, she's the only one with range/distance. So... swings and roundabouts.
This puts me in mind of "Six of one, a half-dozen of the other."
In my little corner of the world, it always meant "something that evens out" and/or "a difference that makes no difference."
So, much like in your example, someone might be weighting the pros and cons of something, or comparing the pros and cons of two different things. When it comes out a wash--the pros even out the cons or both choices have equal good and bad points--it's "six of one, a half-dozen of the other."
"You want pepperoni or chicken on the pizza?"
"Eh, it's six of one and a half dozen of the other."
"If I wash my car today it'll probably rain, but if it does my garden will be brighter. I suppose it's six of one, a half dozen of the other."
That sort of thing. I suppose it really depends on how your character is actually phrasing things, as sometimes the idiom people choose is based in the lead up.