Might be worth re-thinking the questions you need to ask. I would guess that these are important questions for you:
Q: Where can I find out more about Med-Peds?
A:
http://www.medpeds.org . After that site, I suggest talking to the dean(s) of your medical school or leaders in either medicine or pediatrics and asking who in the school/hospital is Med-Peds trained and might be willing to talk to you.
Q: How does Med-Peds training compare to categorical training?
A: Partially answered by the first question, but essentially, Med-Peds attracts a slightly stronger overall group of residents than the individual categorical programs and as a result has very high board pass rates in both specialties. Because of the way Medicine and Pediatrics share overlaps (critcal care, pathophysiology of certain diseases, infectious diseases, etc), Med-Peds doctors are generally well-respected for the diversity of their insight into clinical problems.
Q: How do programs differ in terms of their rigor in Med-Peds?
A: Because Med-Peds has to fit so much into 4 years, the overall curriculum is generally pretty scripted and the only significant variations come down to a month or two of inpatient versus outpatient and the duration of the nominal intern role and the timing that one begins the supervisory role.
Q: How do I find out which programs are strongest?
A: Even more so than in medical school, residency programs in the "top 50" tend to be overwhelmingly difficult to divide based on quality. Frequently, residents choose programs based on location and family rather than just prestige, so you end up with good residents everywhere. The only exception is the occasional program with a particularly weak pediatrics or medicine program in which you may get a different level of educational experience in each. Otherwise most of your learning comes from fellow residents and patient care. What is more important is knowing what your "red flags" are and using that to cut down on the list of programs you'd consider.
Q: What career potential is there in Med-Peds?
A: Greater than 75% of Med-Peds physicians continue to do a combination of the two once out of residency. A similar number do primary care with about 25-33% doing a fellowship, some combined fellowships. Your salary is highly dependent on the details of your job and the location. If you're willing to practice in Nowheresville, Idaho, you could probably get a nicely structured job and pull in $200-250k/year. If you want to practice in paradise, you'll likely be closer to the $150k/year. A typical salary is $150-200k/year. Job details can vary even more widely and are based on hours worked and cross-coverage demanded, which is generally nowhere as intense as residency.