The P90x workouts are based on DVD videos that you watch at home on your TV and workout along with.
If you want to workout in front of your TV 6-7 days per week for 60 to 90 minutes per day, P90x can be a good option for you. But the nutrition plan is pretty tough to follow as the macronutrient ratios change each month. Even a bodybuilder who's used to weighing food would have trouble following it!
Efficient strength training workouts that use compound movements are the foundation of BuiltLean. The program utilizes strength circuits that focus on the largest muscle groups in the body, so you experience the greatest fat burning and muscle building effects. It is arguable, but the BuiltLean workouts are designed to be more efficient than P90x, while still yielding comparable results with much less time investment (3x per week, 30-45 minutes). This BuiltLean workout structure and program has been tested hundreds of times and has been proven to work very well. With BuiltLean, there are no follow-along workout videos. Instead, you have access to exercise demonstration videos in the online portal and printable training sheets that you can take with you anywhere.
If you are already in great shape with a low body-fat percentage and want to work out in front of a TV, P90x could be a great option for you. If you want to get lean and strong and are looking for something that's more sustainable, BuiltLean Transformation is a GREAT program.