If you are talking about only group structure, I would have to agree with you, however, a great many doctors are not in groups, and I'd have to say that in solo or 2 person physician practices, interventional makes more. They rely less on referrals since interventionalists tend to have a great internal medicine patient population, while EP tend to specialize more. Obviously there are exceptions, and exceptions to the exception, however, from what I've seen, I've found this to be the case.