consider the fact that you want to make a comparison, those who do as your doctor says and those that do not. in I, it is one sided, you only study those that do.
moreover, it is vague, drinking wine "regularly" does not mean you drink 1 glass everyday, you can drink less, or more. in either case, you are not doing what the doctor said.
more than that, people who tend to be social drinkers may have habits that the regular population does not have. any of those habits may cause bias results.
now, with all this in mind, what would be your reasons for choosing II?