You Tube sound comparisons

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. 

Miller is right, I did a lot of this kind of youtube listening as well. I always use Grado RS-1 headphones for that, not speakers.
The recording quality should be close for any meaningful comparison.
I didn't compare cartridges and turntables, only amps and speakers.
Of course, you cannot hear anything close to everything there is to hear, but still it can give you a pretty good idea.
One example. Same recording quality recorded by the same people. First, there was all Gryphon system with cd player as a source and Gryphon midrange speakers driven by 300 watt/ch class AB Diablo 300 integrated. It sounded very good. Then, same recording and same system except now it was driven by Gryphon preamp and Class A power amp, both not top of the line. The difference was striking, it was much better. Three times the price, I guess. Was it worth it? Hell yes.
I listened to a lot of speakers in various systems. Didn't like the sound of either Magico or Wilson. Did like a lot the sound of Kharma, Lansche too.
Kharma/Lamm and Kharma/Wavac, both with Purist Audio cabling were super. As was JM Labs Grand Utopia driven by top of the line VAC electronics. Harbeths were very musical but slow with not enough resolution and bass.
So, I wouldn't buy expensive pieces based only on youtube listening but relatively inexpensive I might take a risk with.

I am in the process of recording a bunch of these videos now comparing speakers and amplifiers.  After some testing I have learned that the most important thing in being able to differentiate between speakers and some of the more subtle things in the sound profile is the quality of the microphone used to do the recording.  If they aren't using a good, stereo microphone, the quality of the recording won't deliver.  

For instance, phone recordings, as good as the iPhone and some android phones are, is not good enough to deliver a good experience.   I have learned the actual video is completely pointless and am recording different Video Clips to work in over the top of first rate recorded Audio.  That and getting my wife and daughter out of the house for a day so you can't hear Blippi in the background during recordings.  

You also have to use headphones.  Good headphones make all the difference.