Unsubordinated Debt

Shouldn't that be insubordinated debt? Like...when debt is sassy?

Well...no. If debt is subordinate, it comes below in the ordinal pecking order of bonds in the priority stack, relating who gets paid off first in the case of the "B" word. Uh...no: "bankruptcy."

So an unsubordinated debt means that it's senior-ish. It comes ahead of subordinated debt if a company sucketh the big one and has to have its assets auctioned off. If given a choice, you want to be owning the unsubordinated debt over the subordinated debt. And yes, it'll likely pay a bit less in interest because it is (notionally, at least) less risky.