As a military breh, definitely that 7-3. You have to wake up at 5AM, so that pretty much rules out going to the gym in the morning unless you're trying to skip out on 7-8 hours of sleep. Plus, you're working with all of the higher-ups because lord fukking knows that those bytch ass nikkas aren't coming in for either night (3-11) or mid (11-7) shifts, so you essentially have ALL of your supervisiors hanging around bullshytting all day "supervising."
Mid shift is where it's at. The spot is dead 99.99% of the time, there's nothing to really do after the first 2 hours, and there's usually a single supervisor that doesn't really give a shyt because practically nothing urgent is going to pop up that day shift can't handle

.
And I don't know about the civilian world, but in the military, day shift always gives a shytty passdown to night shift, and leaves work behind without explaining wtf happened, so they have to materialize solutions out from thin air.
fukk that noise.