Both are equally effective ! In different ways
It's hard to say exactly what is better. Because each serves different purposes for different groups of people. As I can see, exercise is often for those who want to gain or lose weight, or in other word, to reach a physical goal, while mediation is one way to seek for the peace and quietness for the soul or mental health. Of course, a healthy body and mind has the closed relationship. It's depending on you whether what you like to follow exercise or meditation, I just cannot give a clear answer :)
I think meditation works better than exercise as it doesn’t require any special equipment nor specific place, even giving 5 minutes time for meditation can lead you to a calm state.
Meditation is for spirit and exercise is a kind of doing sports, so they are different, we need do both of them, if we can, if no you have the choice.
Depends on what you are trying to accomplish.