In both, the majority of your drill time is going to be spent doing healthcare administration. The majority of the job is verifying that people in your unit are medically qualified for military service and deployment. You review annual questionnaires they fill out, follow-up with people who have major medical changes, see people who need to be excused from physical training or need limitations on their duty. If someone has a disqualifying condition, you prepare the medical packet that is processed to either grant them a waiver or be discharged from the military. This is the foundation of medicine in the military.
ARNG is going to be a bit more varied experience because the types of units they have are more varied. Being the physician for a combat unit, a physician for a field hospital, a flight physician, or a physician at a headquarters medical unit are all different experiences which will color what your experience is like during annual training, deployments, and military schools.
ANG is a bit more homogenous with the majority of people doing flight medicine for one aviation unit or another. Being a physician for a fighter unit is certainly going to be different from being a physician for a cargo plane or even an unmanned aerial vehicle unit but there is a lot of overlap.
If you're interested in a MEDEVAC type mission, you're three main options are ARNG MEDEVAC units, ANG CCAT teams, or ANG pararescue units (listed in relative difficulty of getting a position). MEDEVAC and pararescue is going to be more of a medical director job with the occasional chance to jump on board. CCAT is a critical care transport team which is more hands on for the physician.
