I do both- I prefer the mornings and that is usually when I get my 3 runs a week in, but I also like evening workouts since I sometimes let the alarm clock slide. I will say that I feel better if I do a morning workout and it's great to know it's over and done with for the day. I have researched morning verses evenings workouts. In doing so, I came across a term called fasted workouts, which states that you tend to burn more fat on an empty stomach and it also helps improve muscle development, as well as increased fat burning benefits. So, I would say, do what works best for you. If you function best in the morning, workout in the morning. If you work best at night, workout in the evening. I believe either way, your doing something that will make you feel better in the long run...