As an intensivist who trained in emergency medicine and is less than a year out of fellowship working full time ICU at a community hospital, here is my perspective:
Like most people, my medical school rotations were mostly inpatient. I enjoyed everything enough, but was perpetually disappointed by the fact that most of the time patients already had a working diagnosis/plan by the time they were admitted. I did an EM elective during 3rd year and enjoyed the variety, the procedures, and the fact that each patient was a "blank state." Doing the history and physical from scratch was just more satisfying, and made me feel more like a "doctor." As I was applying for residency in fourth year, I did a month in the ICU and enjoyed it, so I kept fellowship in mind.
During residency, like lots of other EM intensivists, I found the critical care to be the most rewarding aspect, but realized that is at most 5-10% of what you do on a day to day basis, and quite often 0%. EM soon lost the "blank slate" appeal and my work ups quickly became very efficient and algorithmic. My medical decision making was a blunt instrument and at the end of the day all I had to decide on was disposition and how to not miss things. So I decided to navigate the quagmire of applying to fellowship as an EM applicant, and ended up doing an internal medicine program. I don't miss EM at all, and the chaos of ICU night shifts (which I fortunately only have to do every couple of months) are more than enough to get the chaos and adrenaline rush of the emergency room.
As to your original question of ICU vs radiology, do you enjoy the more technical or human aspects of medicine? A quote that resonates with me is "Medicine is the most humanistic science and the most scientific humanity," although it falls short in both those realms more often that we would like to admit.
As an ICU doctor, the most satisfying day to day aspect of my work is hearing a patients story (either from them when they can tell it, or their family members), refining a diagnosis, clinical decision making, and helping patients and family's navigate the unpleasantness that comes with hospitalization, critical illness, and/or end of life situations.
I'm perpetually annoyed by all respiratory failure being chalked up to "CHF/COPD/Pneumonia" and treated as such. I love to put my cards on the table and treat the most likely culprit, commit to plan and reassess how the patient responds. I've also undiagnosed COPD and other medical problems that have been perpetuated through the chart, because no one else takes the time to question things (for COPD, its a simple as asking about smoking history, reviewing a chest CT and verifying if PFTs have ever been done). That being said, that's probably more my individual style as a clinician than a reflection of my collective specialty as a whole. My griping may also be applicable to the local culture of the relatively rural hospital at which I work.
The level of detail required to do the job well was intimidating at first, but by now it's easy and I enjoy being thorough and catching things that several other doctors have overlooked.
I'm the doctor that other doctors come to for help, which makes me feel like a highly trained specialist, but I also am a generalist at the end of the day and have to be the one to take full ownership of my patients. The dopamine rush I get when the hospitalist calls me down to help with a rapid response or code blue can be formidable. It's satisfying to show up to a room full of 15-20 people and everyone there recognizes that you're the one in charge. As for procedures, sure they are fun and I will always love intubation, but I could take or leave most lines unless it's in the midst of a "fun" and high-stakes resuscitation. 90% of what I do is think and communicate. Procedures in the ICU can be feast or famine, and there is no guaranteed or steady stream of them, in contrast to IR. I actually consult IR for most of my thoras and paras now, but will do them every once in a while if I think it's best for the patient (such as on the weekend when IR is going to wait until Monday).
As a non-interventional radiologist, my perspective is that your role is much more technical, and there is nothing wrong with that. Your primary role is a consultant, specialist, and proceduralist. Patient and family interactions are quite minimal when compared to those of an intensivist. The IR doctor at my hospital simply copies and pastes my HPI when he writes his consult notes. You for sure will "save the day" and be able to do very cool, necessary, and life-saving things that no one else can, but many of the procedures will be relatively elective/urgent, and very rarely emergent. In my experience, most IR procedures can happen during banking hours. The nature of your work, in my perception, is at the cutting edge of medical progress. Meanwhile in ICU, it's been 20+ years and we still can't decide if steroids work for ARDS. While I love to read new trials and ask questions, a recurring trope in critical care medicine is that every intervention we study ends up making no difference.
Anyway, I've probably missed the boat as by now you have probably made your decision, but this has been a therapeutic exercise for me at the end of a 10 shift stretch, the last 7 of which have been nights (self-imposed).
