Running builds your cardiovascular system orders of magnitude greater than lifting weights does. Running also develops your lower body musculature, especially your calfs and hamstring. If you had to choose one for over all fitness, running is the clear choice.
Coffee Drinker wrote:
The essence of the exercise benefit is muscular strengthening and metabolic conditioning. Training the lower body is especially important for health, appearance, function and maintaining one's mobility throughout life. The superior aesthetic benefits of strength training reflect its superior health and fitness benefits. The muscles are the "window" to the body, including the cardiovascular system, and the best way to improve the health of one's body is to perform high-intensity muscular work.