I'm an IM resident. To answer your question, IM residency isn't bad at all. It's no where close to 80 hrs/wk on average unless on a ICU month but it's still not bad. Most of the time it will be 60-70 hours. Elective months even less.
I'll make the case for IM and provide a different perspective. A lot of residencies are unnecessarily long because we are cheap subsidized labor (there are some on SDN who will argue otherwise but if hospitals were actually losing money on trainees no way in hell they would be increasing spots and lengthening training--revenue drives behavior at the corporate level). A lot of the fields also have terrible job markets--including anesthesiology, radiology, pathology, rad onc, etc--so you have to keep that in mind also. In fact for many of these fields you have to do multiple fellowships just to get a job (just look at their forums) so it's not the case that you'll get a job straight out of residency in some specialities. It's a total scam by the leaders of our fields.
If you love interventional cards (3 + 3 + 1) it is nearly equivalent to what it'll take to be for example an interventional radiologist (5 + 1). IR don't have their own patient referall base so cardiologists are at an advantage and one of the reasons cards was able to steal caths away from IR because IM likes to refer within their own medical specialties if given the option. And like many surgical or procudure based fields, remember IR bread and butter is not sexy--it's draining abscesses, biopsies, doing paracentesis or LPs for services that were too lazy to do it themselves. My point is every field has it's negatives, you really have to find what you enjoy.
As a cardiologist, you'll have job security, great pay, prestige, patients actually get better because of your intervention. Within cardiology alone, there are procedure heavy options both peripherally and coronaries, critical care, imaging, preventive, extensive research, transplant, and even cardio-oncology. Can do mostly inpatient or mostly outpatient or both. Of course there are negatives to cards also (getting called for a chest pain rule out by ER at 3 AM in a 30 yo with a negative troponin x2).
But IM in general has so much inherent flexibility that is not available in some of the fields mentioned in this thread that you'll always have options available to you and you technically can open shop without having to be tied down to a hospital unlike some other specialities. No real geographic limitations. If you want to do inpatient can become a hospitalist for 7 days on 7 days off for 240K after just 3 years of training (which makes it one of the shortest residencies) or can do outpatient work. No other speciality has this flexibility in scope of your work and geographic location, job security and good pay while actually applying what you learned in medical school and feeling like an actual doctor.
