I think you get better training by having a reasonable amount of appropriate off-service rotations. Some things you just aren't going to see enough of in the ED, so doing time on that service really helps. Example - labor and delivery.
Medicine floor month sucks - no way around that, but it DOES help build relationships with your medicine colleagues which makes admitting patients to the medicine floor WAY easier (hard to be a jerk and block an admission from your friend).
In my program (Wash U in St Louis) we do cardiothoriacic ICU (put in a TON of chest tubes all month) neuro/neurosurg ICU (managing mannitol, head bleeds, bolts etc), peds ICU, surgical ICU, radiology, toxicology, orthopaedics, L&D, surgery peds and medicine floor (1 month each).
For each of the rotations I have done I have learned SOMETHING that has helped me at some point in the ED - something that I could not have learned from doing every day in the ED alone.