I think there's an argument to be made for expectations of a student's specialty specific knowledge base being lower in EM than in surgery. In terms of the actual specialties' knowledge base, there is no specialty whose knowledge base completely overlaps or is completely overlapped by another specialty. That's sort of the whole point of specialization. Whether one specialty is "easier" than another (which is probably a more useful question) is going to depend a lot on work environment and your tolerance for the day to day of a specialty (which I think med school does an extremely poor job of supplying). Anything else is basically like trying to argue that an apple is less of a fruit than an orange.
