As Quoted from Two Bros FAQ Site:

Both products do a similar thing but in different ways. The Juice Box is designed for customers who want a simple and cost effective fuel injection solution to increase the performance of their vehicle with as little effort as possible. TBR Juice Box
• Costs $299.98 which is $60 less than the Power Commander
• Pre-programmed by TBR to maximize the performance of TBR exhaust systems
• Does not require the use of a computer to make adjustments
• Increases horse power
• Improves throttle response
• Improves smoothness while cruising
• If the Juice Box is faulty, the vehicle will revert back to its stock running condition and the LEDs on the Juice Box will indicate a fault
• Load Based technology increases performance while maintaining fuel economy
• Is plug and play with OEM style connectors with no wire tapping required
• Has 3 to 6 simple color coded push button adjustment modes to make simple but effective adjustments to the vehicles fuel curve
• Smallest and lightest product of its kind on the market
• Race Only and Road Legal Versions are available The Power Commander III and V
• Costs $359 which is $60 more than the Juice Box
• Does not come pre-programmed with a map to maximize performance of TBR exhaust systems
• Does require the use of a computer to make adjustments
• Maps can be downloaded from online and loaded into the Power Commander using a computer
• What is recommended is a Dynojet Tuning Center for tuning with Dynojet's Tuning Link Software which typically costs another $300-$400
• Increases horse power
• Improves throttle response
• Improves smoothness while cruising
• If the Power Commander is faulty, the vehicle will not run until the Power Commander is removed from the vehicle
• Does not have Load Based technology to increase performance while maintaining fuel economy
• Is semi plug and play with OEM style connectors but does require wire tapping the TPS wire with the risk of damaging the OEM wire
• Has thousands of cells in a spreadsheet that each have to be adjusted to adjust the vehicles fuel curve properly
• Larger and heavier than the Juice Box
• Race Only and Road Legal Versions are available