Ladder workouts allow you to do more work in less time, without feeling like more work. By never training to failure you can also work out more often, thus increasing strength faster.
You never use extremely heavy weights or go to failure, thus being healthier for your joints. You will still get stronger if you put the work in.
Working out with the app allows you to do more work in less time. It also allows you to stay focused on doing the work, not on sets and reps.