I tested out the grinder with the help of my kind assistant, Franklin.
Frank took 3 headshoots to kill, which is the same as my auto 10 but without a flash light and a slower fire rate. It does have the benefit of craftable ammo though, and of the 3 shots that hit, I retrieved 2 so the disk break chances cant be too terrible if youre not bouncing them. Its also worth noting that Frank was the lowest level of grunt, and the damage discrepancy will become more important when fighting higher level enemies with more health, but vs the next tier up on the smg guy with a helmet around the corner felt compairable to the auto 10 too.
Verdict: both, both is good. The grinder is cheap to run and is great at feeding the pistol, and the ghetto blaster is my favorite backup flashlight.

But also: What is up with that hitbox shenanigans?