An emergency physician can run circles around any other type of doctor -- including a cardiologist -- when treating a cardiac arrest. They can stitch wounds in one room and decompress collapsed lungs in another. ER docs can prescribe antibiotics for the 25 or so most common infections by memory. What an ER doc is not good for is taking care of -- or even recognizing -- rare diseases and conditions. You don't go to an emergency doc hoping she'll diagnose MS or cancer. It happens sometimes or, more to the point, they sometimes will identify a problem and send you to a specialist.