I would make a list of the things that you like/dislike about both fields. For me, IM and neurology were my two favorite rotations but I chose neurology for a couple of important reasons.
1. General Medicine was just not specific enough. I wanted to be an expert in a specific organ system and not just a generalist. General medicine floor and clinic services frustrated me because these physicians' knowledge/expertise was limited. True, they are masters at common illnesses and their common presentations, but when things got sticky, we often had to call in the specialists. This was a big problem for me, and was a key reason why I decided to become a specialist. I want to be the person who is called when the first line of physicians are clueless or need help with management. I figured, like you, if I was to choose internal medicine I would have to obtain a fellowship to fulfill my career goals.
2. IM Specialities vs Neurology. Because I knew I wanted to be a specialist, I compared the various internal specialties to neurology. I liked endocrinology, cardio, and pulmonology. So then I asked would I rather become an expert in any one of these specialities or neurology. And while all these specialities are cool, I soon realized that neurology was just more fascinating. I would rather spend all night reading about multiple sclerosis/alzheimer's management than treatment plans for diabetes or heart disease or pneumoconiosis. This is an important point. You are getting ready to chose a field that you will spend 30-40 years attempting to master!! Ask yourself which field can keep your interest for that long. For me, neurology is the only field that can keep my interest in so many different ways. Which will it be for you?
3. Neurology Patients. While all physicians deal with sick people, neurology patients have a specific set of problems/issues. This can be either a good or bad thing depending on who you ask. Neuro patients often present with an illness that not only causes concern, but often causes disability. These patients have difficulty talking, walking, moving, remembering, and interacting with the world. Not everybody wants to deal with this on a daily basis. Many neurologic diseases can be devastating, and it takes a special type of physician to deal with these complaints and find pleasure in helping people with these issues.
4. Treatment Options. I am sure you have heard that neurology is a "diagnose and adios" field, but this is not as true as many people think. Many people told me that neurologists do not treat anything and most of my patients would never get better if I become a neurologist. This statement is not true. True if you go into a surgical field, you can "fix" many things, but in medicine this is not usually the case. Lets name the most common diseases seen in neurology: headache, seizures, dementia, parkinson's, & stroke. We have very good treatment options for all of these diseases that can greatly improve the quality of a person's life (with the exception of Alzheimer's). And while neurology treatments are not often cures, I believe neurologists are able to improve the morbidity of disease just as good as any other medical specialist. Compare this list to common diseases in cards, endo, or pulmonology. I state that the overall improvement seen in neuro patients is similar to that seen in IM specialties. How many patients do you know that keep their diabetes under control or see improvement from their emphysema? Medicine is full of non-compliant patients and poor treatment outcomes regardless of the field you choose. The question that you should ask yourself is "Which field has treatment plans that are most interesting to you?" Would you rather track a persons A1c or the depakote levels? Would you rather interpret brain MRIs or colonoscopies? Would you rather decipher EEGs or ECGs? This is more of a personal preference.
5. Neuro Exam. Do you like performing a complete neuro exam? Do you enjoy the cerebral activity of using clinical skills to identify and localize abnormalities. The neurologic exam is very detailed and it takes a keen observer/ examiner to be successful. Not everyone likes this.
6.Future of Neurology. The brain is the last frontier of medicine, and many expect our knowledge of the nervous system to greatly expand in the coming decades. You mentioned that you are interested in academics. Do you want to be a leader in the development of new knowledge in neurology? Do you enjoy neurology research? Do you enjoy teaching neuroscience/ clinical neurology to students? These are other important questions you should ask as you make a decision.
7. Talk to mentors. If you are really having a hard time, talk to a mentor to further hash out your career goals. It always helps to discuss these things with people who know you well.
