ID is not particularly competitive. The downside is a lot of HIV work in most parts of the country. In many places and larger cities it might be nothing but HIV clinic several days a week. The other downside I think (I'm in IM but no ID) is that you may be at the mercy of other physicians for consult work.
Most ID Fellowships require 1 year of clinical work and 1 year of research. It has to be a 2 yr fellowship to qualify for the certification exam.
Neville Sarkari
IM Attending/Private Practice