only MY opinions after having done a residency and fellowship
General peds
Pros:
patients are generally healthy, so a happy environment
wide open job market with many opportunities
Cons:
Boring...patients generally get better on their own
low pay ( compared to other fields)
parents are neurotic ( obsessed with their constipatred toddlers)
Subspecialty peds:
Pros:
patients are generally sicker ( not boring)
better $ opportunities thant gen peds ( usually )
you don't have to treat things you don't like ( I don't like whiney toddlers or teenagers, so I just do newborns)
Cons:
weaker job market ( in some specialties) and you might not be able to get a job in the city you want, or be forced to do academic medicine ( lower pay)
3 years fellowship where you may have to do significant research
you forget a lot of what you learned in residency, except the area you specialize
of course I am biased toweards subspecialization because that is what worked for ME.
Many of my friends from residency are in general pediatric practice, adn are very happy. Being a general pediatrician was just NOT for me. I go crazy when I am surrounded by things that don't need to be fixed
the best thing to do is a residency. you get to rotate through various subspecialty areas, and try to decide if you can ONLY do that field for the rest of your life. you don't HAVE to be cornered though because I know a peds cardiologist that does part time peds cardiology a few days a week, and a few days a week does general peds in another office ( you can bet none of the kids in that office get referrals for evaluation of murmurs!~ )