Best? The one you like the most of course. One of my residents insists Rheumatology is the best, the other won't agree on anything other than cardiology.
Most subspecialties are in heavy demand, especially in academic settings. Cardiology, Gastroenterology and Nephrology seem to be in wide demand nation-wide, with the others in slightly less demand.
Salary varies by area. If you go to a densley saturated area on the coasts (Boston, SF) you might make less, in relative as well as absolute terms than if you work in an relatively poorly saturated area. Eg, our graduating GI and Cards fellows are getting offers of 280,000-300,000+ locally.
