The main difference is after Medical School. The Army National Guard can only slot what is available in the state they support. While in Medical school, do you know what state you will be completing residency in? What is to say you enjoy the location that your medical school or residency take you too? The Army Reserve is a federal entity. If the unit near where you live does not have a slot, or vacancy for your specialty, you are eligible to become a unit member of the Army Personnel Management Command. You will attend weekend Battle assemblies locally, but your two weeks of annual training, or any operational assignments will be in your specialty. The weekend Battle Assemblies are typically administrative and very little patient care, unless you are in a unit that conducts their Battle Assemblies, or a portion of their Battle Assemblies at an Army Treatment Facility or contracted Civilian Facility. Rather than either 1. Having to travel to a different state to serve in your specialty or 2. Being assigned as a GMO, the Army Reserve will utilize you for your skill. The community aspect of the National Guard is the same in the Army Reserve. You will still serve locally for the most part. The Army as a whole is huge on the community relations aspect. The DIMA program is only open to Prior Service physicians because of the complexity of the program. It takes someone that understands the Army structure to fully understand the requirements. I have personally transitioned several residents into the Army Reserve from the National Guard because of the vacancy issue, which is a repeat of the lengthy application process. The type of assignments you will be placed in the Army Reserve can be phenomenal, to include but not limited to, International Humanitarian Aid missions, Joint force missions with partnering countries, International Disaster Relief, Augmented missions, and much more. Embrace the Challenge, Live the Adventure, and enjoy your service to the fullest extent.