Although to be fair, most of the time the ER docs get the easiest part of the obnoxious patient's care. They say **** it and admit the fake seizure or fake sickle cell crisis or back pain or belly pain or arm numbness or whatever the hell else, and they are probably doing the right thing. I mean they can't necessarily tell if a patient's faking it and it's easy as hell to just turf them up to the floor. The people who really get the crappy jobs dealing with these problem patients are whoever they get turfed to, whoever gets a stupid consult, and the hospital, who has to swallow the 3 day hospital stay, nursing care (high-maintenance), a CT, an MRI, a handful of labs, and all to settle on our diagnosis of exclusion - which was the ER guy's hunch to begin with - that there's nothing wrong with them.
I don't think we should get into the whole discussion about missing diagnoses and "faking" illness and all that, but I'm just saying, in private practice, yeah ER docs are stuck with every patient who walks in the door where most others can stay the hell away. But in training, academic medicine, and hospital employment, ER docs get the easy job of flipping a coin or whatever they do to decide whether to admit or send 'em packing, either way it's no longer their problem, unless they come in again, and even then chances are 50:50 it won't be on their shift.
To address the OP's question - residency is not like medical school, where basically you get the exact same education wherever you go, +/- a few research opportunities or better/worse rotation or two sprinkled in, and they're closely watched by the LCME to make sure. The ACGME is the accrediting body for residencies, and as was already stated, they don't go to lengths to ensure all residencies are equal, residencies are not all equal. Read up in the residency application forums, people are talking about whether they prefer a hospital with lots of trauma vs. very little trauma, with fellowships in-house (with resulting better ins to fellowship but perhaps less access to those cases pre-fellowship), different call schedules, dedicated research years, case volume, ....there's a concept of a "gentleman's program", etc. So the point is that there's a lot more that goes into the decision of where the "best" place to do residency is than where the "best place to do medical school is.
The best place to do medical school is the school with the best reputation unless you've got some compelling reason to go elsewhere. The best place to do residency is really really subjective and depends on your goals and preferences, and those come in a wide variety.