For me, both. I chose a BMI that was in the middle of the normal range. When I was a young adult, I was very thin. As I got older, I gained weight, but tended to stablilize at about 120lbs, which is my goal weight at this time, and corresponds to a BMI of 22-23. (My weight was about 95-100 lbs from the time I was in junior high until I got out of college; when I started graduate school, and got married, it was very difficult to maintain such a low weight). I was very comfortable and happy at 120 lbs, which I last weighed about 8 years ago. I think that the new standard for ideal weight, also, is a BMI of 22 or so.
For me, it is a happy coincidence that a weight I am comfortable with and able to maintain is close to my ideal weight. If there was a difference, I would go for a weight that I was comfortable with and able to maintain. I wouldn't exert the effort, for example, to get to a weight of 110, for example, because I know I'm not able to maintain that without excessive effort. As long as a weight is in a healthy range, I think it is OK. This is anywhere from a BMI of 19 to 27. There is no excess morbidity for a BMI of 27, although a BMI of 25-27 is overweight.