I would choose whichever major that fits ALL of these criteria:
1) You will enjoy doing the school work,
2) You will enjoy doing the work for 40 years after school,
3) The major actually gets you a job,
4) The job obtained earns enough income that you will be satisfied.
The answer may be neither law school nor medical school.
Lets apply these to your two choices:
1) Will you enjoy sitting down eight hours a day memorizing lists? Can you do that day in and day out for eight or so years nonstop? If you answered no to either of these then you won't finish medical school. It doesn't matter if finishing medical school will be rewarding or better overall - since you never graduate.
2) When installing a program, do you enjoy reading the license agreement in full, or do you just click accept? If you don't like reading that then you won't enjoy doing that for 40 years as a lawyer (courtroom time is minimal compared to the time you spend reading those over and over and over again).
3) Obviously #3 is satisfied for both majors.
4) But is #4 satisfied? As a public defender you'll make next to nothing, but as a partnership in a big law firm you will make a killing. Same goes with doctors. I know several doctors that are general practitioners with their own office that make next to nothing - but surgeons often make a killing.