as an ED doc and an ICU doc I agree with both of you, but I do think the ED scope of CC is very narrow. The initial resus is fun lots of prcoedures and keeping the patient alive, which is why you went into ED in the first place. ICU is more about being OCD about everything: riding out AKI (should we start CVVH), hypoxemic respiratory failure on high FiO2/PEEP, MODS, VAP, DVT/PE from immobility, poor nutrition or intolerance, GIB, line infections, delirium, weakness/debility, when to stop antibiotics or restart for that matter is the daily grind of critical care. ED docs have no desire to do this, and ICU docs have no desire to sift through low risk chest pain, low risk abdominal pain and social complaints. We both like to do resuscitation which is where the venn diagram overlaps and both specialties are excellent at this, unfortunately it represents a small portion of both practices.
The ED at most places is NOT set up to take care of critically ill patients for any prolonged period of time. If you do not have a cc pod with excellent protocols in place, dedicated nursing ratios of atleast 1:2, after the initial resus that patients excellent care you just gave over the initial 1-2 hours is likely to dramatically decline. This isn't because the ED is incompetent (no matter what the admitting team says) it's because you have a thousand other things to do, and the busy ed is not the place to be OCD about ICU patients.