Duke has a lot better fellowship matches, last time I looked. I heard they used to be intense, maybe a bit malignant, though they are known for good clinical training and have some big names in cardiology and some other areas. They get respect in the SE and on the east coast to an extent. Yale is more of a regional northeastern place. It's probably good but doesn't have quite the "name" of Yale undergrad, if you want to rank versus other hospitals and residency programs. If you want to stay in the NE, there might be the same or greater opportunity to make faculty connections, etc. at Yale, though. It might matter what subspecialty you want to do also. I'm not sure what Yale is known for. Duke is known for cardiology, particularly interventional and I think also outcomes and maybe some other areas of clinical research.