Many Atmos/DTS:X Sound formats are only avaiable on UHD. So theres that. For me sound is about 100x more important then Picture.
Then Youtube as a medium is incapable of demonstrating the diffrences because the biggest diffrence is HDR, wider range or color. YouTube has a sucky way of compressing youtube and either theres HDR enabled, then the BluRay is not native or it isnt HDR then the UHD is not native.
The comparison also is completly useless ( i watch them as well for a few things, like resolution or something but i have in mind that its basicly useless )
So you have to make up your mind yourself. There are many, many bad UHD discs out there which are just poorly upscaled BluRay discs so you have to inform yourself with 3rd party websites that test those Discs and tell u what are good and what are bad UHD discs.