As pp mentioned, it might help if you tell us more about your goals. I love both HIIT and Intensity.
HIIT has three 30 minute workouts; all are tough interval style workouts. HIIT is great for interval training, for getting in a great cardio workout in a short amount of time and the fact that you have three workout choices on one video.
Intensity is one of my favorites - you have the separate step portion (tough!), then the two HIITs - each are about ten minutes, one is low-intensity and one is high intensity and then the bonus boot camp. You have all the fabulous premixes (nine in all I think?) so you have lots of choices from one DVD. I really love both, but if I *had* to choose I guess I would go with Intensity for the variety. That said, if I had to choose timesaver cardio I would definitely go with HIIT.
Note that you need a step to take full advantage of both workouts.