Basically whichever one you like—mix it up, keep it fresh but go at high intensity for the best results if weight loss is the goal. Make sure you increase your intensity only as you can. For more info, see below:
What is the difference between high and low-intensity exercise?
• Low-intensity cardiovascular exercise (40 to 50 percent of V02 max. or 60 to 65 percent of your max. heart rate) burns fewer total calories but a higher percentage of fat calories than high-intensity exercise, measured for the same amount of time.
• High-intensity cardiovascular exercise (60 to 80 percent of V02 max. or 80 to 85 percent of your max. heart rate) burns more total calories in less time and more absolute fat calories than low-intensity exercise.
• With the goal of body fat loss, higher-intensity exercise yields the same results as lower-intensity exercise, but in a shorter period of time.
Guidelines for proper cardiovascular intensity for fat loss
• Novice exercisers should work within 50 to 60 percent of their maximum heart rate.
• Once you adapt to an exercise intensity level, it is helpful to increase your workout intensity. Changing the intensity and/or duration of your aerobic workout every two weeks helps you avoid plateaus and continue to lose body fat.
If your goal is body fat loss, higher-intensity exercise yields the same results as lower-intensity exercise, but in a shorter period of time. In order to keep the body in an adaptation phase, the mode and intensity of aerobic training should be changed every two weeks.