Hi,
Really a nice informative article and a good differentiation between these exercises. Swimming is most useful for the peoples at old age, peoples recovered post injury, knee problems, as swimming is a non weight bearing exercises which help to improve strength and loose fat without staining any joints. Running is a for the fit peoples who are very much used to normal basic exercises while cycling again is a good option for old age peoples, peoples with knee injuries. etc and can improve your endurance and burn calories.

Good one