So, after reading all of this thread so far, I am assuming you are talking about the preload shift. I've never heard of Sunrise, myself. Our preload shift is from 4:15-8:00AM. But realistically, we're usually not done until 8:30, and typically, I don't leave until 8:45, because I go help other 'areas'.
I don't know much about the other shift that loads outbound trailers, so I can't compare the difficulty between the two.
At my center, the turnover rate is pretty high for preload. I see tour groups come through about once every few weeks (usually around 7am). And every couple of months, I will see new hires standing near the entrance, waiting for their 'assignment'. In fact, I saw one guy today, and two weeks ago there were two other guys... so maybe it's even more frequent.
There were four of us in my training 'class'. One guy got picked for unloading, the rest of us were going to be loaders. They make this decision by eye; my guess is whoever looks more (physically) fit goes to unloading.
You mentioned that you were told that unloaders are expected to do 1400 pieces, and loaders 500? That seems unreasonably low. I always thought unloaders are supposed to move something like 1000 pieces her HOUR? Maybe it depends on what type of system you guys have setup over there. Is it a 'boxline' like some other guy mentioned? I think boxlines only have one belt? I don't know, I'm only familiar with what we have here. We have seven belts, and packages don't travel along a conveyer in front of us. They travel across belts in the back and up above, and come down a slide to our respective sorting areas. We have single package cars that get 400+ piece days. I think the typical piece count per area (usually about 3 package cars) for us is about 700-1200.
There are slow days, busy days, and normal days. Anyone who says there are no slow days either works at a busier center, or is just making things out to be more difficult than they really are. For us, slow days can be a result of a couple of things. Such as, not enough people showed up for unloading that morning, or a low piece piece count for the center that day.
Our supervisors do not wear vests; they wear red-ish or green shirts. Only the guys who work out in the 'yard' wear vests here.