Re: Dave 126.
No. Just NO!
The OLED provides better dynamic range. (Black has always been black, white has always been white, everything else is false advertising)
The OLED has better colour reproduction. (Green is green, red is red etc, everything else is false advertising)
The UHD/4K provides better resolution.
The resolution alone is a nice touch, it is an improvement as with all things. It is down to personal taste and specific content on if this is needed or wanted (for example I like it, but others wear glasses and see no benefit).
But how does it offer "greater dynamic range"? It is a TV with pre-recorded content, OLED and black is black, white is white. How can they "increase" that via the source data or by changing from 8bit to 10bit colour? They can't. ;)
BUT, the 4K does offer finer colour range. So sunsets and subtle colour gradients have no banding. But to be honest, I've only ever seen banding on PC games/webpages, never on TV content as this naturally provides dithering that even at SD is perceivable.
TL:DR, the advertisers and marketers are very good at using the wrong words to describe real changes, and you seem to have fallen for it. AFAIK they even back ported some firmware to add High Dynamic Range to HD TVs (you saw a real change, colour improvement and contrast from the OLED/backlights in LED, the marketers lied and said it was a 4k improvement only).