Doing more repetitions with lighter weights will help you build up Muscle Endurance. And the truth is, in the real world, you will use both in your everyday life. Muscle Strength is the ability to exert a maximal amount of force for a short period of time.
Examples of muscular strength includes pushups, squats and pull ups. The general rule for strength is 3 sets of 5 to 8 repetitions for building strength. You can add more weight to increase strength. The same exercises used to build strength can also be used to build endurance. The longer you maintain the exercises, the more endurance you have. Going from one exercise to another with little or no rest will get your body used to working for a long time.