Why when I use airplay with my Apple TV and MBP retina I see lagging audio delays and pixelation in my MBP retina screen

Why when I try and use airplay from my mac book pro retina , it is extremely slow, and if I try and stream a movie or something its that terrible it is unwatchable and usually freezes then stops. I see pixelation in my MBP retina screen, when I move the mouse in my MBP retina I see blocks. But I don't have any issue with airplay when I use iPhone 5 or iPad mini