So what's the story here? Well, optimal streaming is achieved by making use of all the available bandwidth in the system. Why stream just from the hard drive when you can run in data simultaneously from both the disc and the HDD? Based on what we're seeing on the Xbox 360 version, perhaps running both DVD and HDD assets from just the one source slows down access times, impacting streaming performance. It's not game-breaking stuff, but it does take you out of the moment when it does manifest and for that reason we can't recommend installing the play disc.