Takes BluRay to tell any real difference. BUT most 4k TV's have
240mhz minimum refresh rates pumped up to over a thousand that definitely improve action or motion.... like a football or baseball being thrown... on large screen TV's. On slower TV's those can seem to "checker" across the screen; just not quite seamlessly smooth. 4k screens have improved blacks and dark grays but even then it's hard to tell a difference with normal viewing but with demand movies you can see some improvement. They look really great in stores in demo mode especially beside an older screen. Make sure the unit you're looking at is adjusted for "normal" brightness and so is the screen next to it. If the store is brightly lit (most are) adjust both brightness settings simultaneously. This is an old trick to get you to spend more.