You Tube sound comparisons

Wish they would do shorter segments, ie. 15 seconds vs 15 seconds of same music section.  Makes it easier to compare.

No, that is a crutch that makes it harder for you to learn HOW to compare!  
That is exactly why I said,

Don't focus on any one thing in particular. Just listen to the music. After a while I think you will see what I mean. Be patient. Give it some time. 

The level of listening you are doing when comparing little bitty samples of tracks is a completely different process from what it takes to absorb the full meaning conveyed in each case. All you do with your few seconds is focus on one itty bitty little aspect of the sound. If you listen this way then yes the videos are pointless. But listening this way ALL auditions are pointless! You must elevate yourself to a level where you are getting in tune with the whole presentation. I'm not saying this is easy. Few things worth doing are. But if you can learn to do it- wow. Whole new world.

Obviously what you hear is a far cry from the actual in the room sound. Still, if you listen after a while you can get a pretty good sense. Surprisingly good. I started with this Let There Be Sound! channel that helped me a lot buying my Koetsu Black Goldline and Herron phono stage. Even though that's not what its about, still after listening to several different records being played on the different rigs I got a real good sense of their character. In my room and system of course its in another universe. But still it sounds familiar. Same for listening to Moabs. There's a couple good Synergistic demo's too. 

I suggest listening to a number of these https://www.youtube.com/channel/UCOMFDF7QgMDj88bbSCzAXSg Listen to ones with the same cartridge and stage first, then compare to different carts and stages. They aren't really true comparisons. The recordings are all different. But pay attention to the components while listening. Don't focus on any one thing in particular. Just listen to the music. After a while I think you will see what I mean. Maybe go find the same tracks elsewhere, off CD or whatever. Just to get used to the idea of comparing on a laptop. Or with phones. Be patient. Give it some time. I think you will get the hang of it and after a while be surprised how well it works.