Geriatrics Fellow here. I was IM trained and I am in an IM Geriatrics program.
1. It depends on your career goals. Are you interested in academic medicine, medical education, or medical directorship? Do you want to limit your practice to seeing older complex patients?
2. As FM you can apply to both IM and FM Geriatrics programs. AAFP considers Geriatrics a CAQ for FM vs. ABIM which considers it a board certified specialty for IM. My Geriatrics rotation during residency was at an FM Geriatrics program. It was more clinical w/ less QI/academics/research, and had more outpatient than inpatient months. I am currently training in an IM Geriatrics program. There is a focus on QI/academics/research, and we have more inpatient than outpatient months. Honestly, I feel I should have done an FM program as this was my pivot toward outpatient work and was not very interested in QI/research.