In the short-term, exercise can be a tool to build muscle or reduce fat. But for a person to continue exercising over the long-term, it has to be enjoyable in my view.
Said differently, the goal of any exercise session is that it gets you to come back next time.
I still go out and run 2-3 times a week the same as I did 20 years ago. Yes, I want to be healthy, but I exercise primarily because I enjoy the exercise sessions themselves.
Do whatever you like as long as it is enjoyable. Enjoyment trumps all in the long-run.