DV and HDR10+ dynamic metadata makes tonemapping content that is potentially outside your display's capabilities better (as HDR10 does to a lesser degree). However some manufacturers ignore the metadata (for HDR10 at least - treating it as PQ10) and use their own algorithms instead of using metadata information. (*)
Ironically DV and HDR10/10+ are based on PQ and a direct 1:1 link between video level and pixel nit light output - HLG isn't (it doesn't mandate a 1:1 mapping between video level and light output - it's relative instead), and HLG has built-in support for ambient light level compensation. Dolby have had to accept that PQ doesn't work for some viewing scenarios and use DV IQ to do something similar to what HLG can do.
Personally if DV and HDR10+ can improve my TV's peformance I'm happy to take it - but I'm not going to spend LOTS of money chasing after support for them. That said not having DV did partially influence me not to buy a Samsung Quantum Dot OLED - I've gone for an LG C3 (65").
(*) Some DV profiles use ICtCp colour space instead of YCbCr/YUV which can in theory improve picture quality as it better maps the high and low bandwidth channels to match the eye/brain perception - and also comes closer to constant luminance (I think) - which has always been an issue with YCbCr/YUV vs RGB gamma processing (I think). Other DV implementations use YCbCr/YUV HDR10/10+ base layers and add an enhancement layer to get nearer 12-bit representation rather than 10-bit - which can also help (You don't need a 12-bit capable display for the benefit as you'll get some benefits with tonemapped 12-bit content mapped to a reduced range 10-bit display I think)