The 1080p Blu-ray has a much higher bitrate (25-30 Mbps) than streaming. A good 4K TV will upscale this to near-4K quality, especially with HDR simulation mode enabled.
When combined, these features create a viewing experience that's unparalleled in home entertainment. For a film like TRON: Legacy, which relies heavily on its visual effects and futuristic world-building, 4K HDR is the perfect format.