I think you made the right choice in not applying to med/peds programs. If you're confident about subspecializing then it really doesn't make much sense to do the extra year of training, while thereby also limiting your exposure to the field you end up choosing (you definitely miss out on certain things by choosing a combined residency). I almost made the mistake of choosing med/peds because I too couldn't decide, but in retrospect I'm VERY glad I bit the bullet and made up my mind ahead of time. I've already seen a number of residents who trained in med/peds go on to never practice one of the two specialties, or do a subspecialty fellowship in only an adult or pediatric field. It very much sounds like you'd be one of these people, so I think you made a smart move.
Now comes the tough part of deciding between the two. Obviously no one can make this difficult decision for you, but hopefully some of our comments and reflections here will be somewhat helpful. I'd like to add a few observations to the mix:
Some of your assertions about the practice of medicine aren't all that accurate or fair. For example, I wouldn't agree with your implied generalization that adult patients mostly don't get better, or that pediatricians are more satisfied than adult docs. Indeed, adult patients are often much more grateful and more invested in their healthcare than children, and we cure so many conditions on a daily basis. These range from the routine and mundane, such as UTIs, bronchitis, or pneumonia, to the more complex, serious, or obscure, such as meningitis, NPH, Guillain-Barre, ITP, TTP, SVT (which can often be catheter-ablated now), etc. etc. The conditions we diagnose and treat can have a catastrophic effect on a person's life, arguably more so than the common pediatric conditions, so we stand to make a very significant impact on our patients' lives. Sure, some people will never quit smoking or won't take their BP meds, but these won't define your existence as an internist any more than child abusers would define your existence as a pediatrician (unless you let yourself become a debbie-downer and allow them to, which certainly happens to some docs). There's also quite a bit of chronic disease management in the peds world, so I wouldn't use your preconceptions about chronic disease management as a deal-breaker. Think asthma, ADHD, CF, cardiac defects, cerebral palsy, autism, genetic syndromes, short gut, etc. etc. You'll face this in just about any specialty, in medicine or pediatrics, and chances are you'll like it in the end.
Regarding the improvement and treatability of conditions in adults, consider all the quality of life improvements and life extension provided by cardiologists and oncologists. Many people are cured of their cancers, and many people are given decades of additional life through cardiac interventions or other medical therapies. Sure, their CAD may never go away, but this provides you with a wonderful opportunity to develop longitudinal relationships with grateful patients who you can help a great deal, and who will love you for it. It's a very special thing actually. Adult physicians do TONS of good for their patients...we're not all just wasting our time treating patients who won't help themselves. And while I agree that many primary care doctors are dissatisfied, perhaps more so in medicine than pediatrics, this shouldn't be a big consideration for you if you're planning to pursue subspecialty practice. I've found subspecialists to be much more satisfied with their careers and lifestyles compared to PCPs for sure, but also compared to many pediatricians I've met. Plus, the dissatisfaction is more so due to time-pressures that are driven by reimbursement problems, forcing PCPs to see more patients during a clinic session, rather than unhappiness with adult medicine itself.
I guess my take-home message here is this: be careful about the assumptions you make in this process. I think several of your initial observations are inaccurate, and have the potential to mislead you greatly. Instead, I'd recommend that you explore your "gut feeling" more. It's very important to listen to these feelings, as there are often some very important considerations underlying them. That said, my gut feeling led me astray, and it caused me to almost make the big mistake of applying to med/peds when in retrospect medicine was by far the best choice for me.
What ultimately helped me make the decision was thinking more short term, about what it would mean for my daily experience throughout the next 3-4 years of my life. Ask yourself, what's the training like? Does it appeal to you? Why or why not? This may help you get to the root of your initial impressions about what specialt appeals to you and why. This actually made it quite clear which path was the right one for me. I realized that I loved the "idea" of pediatric subspecialty practice, but when I thought about the reality of the daily peds training I realized I would've hated about 3/4 of it. I didn't like NICU, was terrified by the idea of PICU, found the nursery to be boring, didn't like the mundane nature of well-child visits, didn't like the overbearing parents, hated the snotty nose clinic and vaccinations, and didn't like the simplicity of most of the disease processes. But I loved the complex ID stuff on the wards, the differential diagnosis, the short gut management, genetic diseases, heme/onc, cardiology, etc. I thought this meant that I loved subspecialty peds, but really what it meant was that I loved certain features of subspecialty practice, which are present actually in both medicine and pediatrics, and that the "peds" part of it was actually more of a negative for me. In the end, I recognized that what I liked about subspecialty peds was actually the complexity of the diagnosis, treatment, and management, and NOT the actual pediatrics part. Then when I thought about medicine some more, I realized that every day was especially enjoyable to me because there was just so much to know and master, so many diagnostic possibilities and challenges, and so many ways to help patients, whom I felt I could interact with on a much more meaningful level, and develop longitudinal relationships with.
Sorry that's a bit of a long-winded reply, but I hope it helps give you an example of my own journey and thought process in a quite similar situation just a few years ago. Good luck with the decision! (and keep us posted 🙂)
