I am currently in my second level internship in Chicago at an urban hospital.
What you would be doing in a hospital varies from hospital to hospital, and even moreso with department to department. In cardiology you would do a lot of discharge planning and working with hospice placements, and skilled nursing facility placements. You also would spend little time with the patients and do a lot of paperwork/notes. With oncology it will be more long term and a bit more clinical/therapeutic. You do some discharging and a lot of psychosocials. Unfortunately there is a high mortality rate among oncology patients. With the emergency department it will be short term, crisis interventions, and you will do everything from psychosocials to housing assistance, dv cases, DCFS cases etc.
Basically hospital social work pays well, but it is largely made up of chasing MD's, doing discharges, and paperwork...and doing discharges, a lot of them. It can be great if you are in the right department. I hated doing cardiology but loved both oncology and the ED.