Hi William,
my preference would be for Soundcloud rather than YouTube and I think they are probably both worth using (rather than just hosting the sounds on your own website). I don't know about the USA however I know that Ireland's music licensing and copyright society is now paying out on plays via Youtube. I don't have the exact details on how the payments are calculated however on the page linked (http://www.imro.ie/music-creators/imro-distribution-policies/imro-distribution-schedule/distribution-d124/) if you scroll down to the bottom you can see that there are now streaming payments backdated from 2009 up to 2012. I'd imagine the numbers are pretty low for anything classical (or for my commercial CD) however the way I look at these things is that it is better off in your pocket than in some of the bigger record company's pockets.
In terms of why I think Soundcloud is better than Youtube, I uploaded the preview tracks for my CD onto Soundcloud and linked them back to my website (http://www.tommcelvogue.com/index.php/home-page/music/new-cd/). What this gives me for the minimum premium package on soundcloud (€66 per year - solo account) and a free google analytics account is information on how many plays I'm getting on the various tracks (via Soundcloud stats) and where these plays are coming from (via Google Analytics). It's not perfect but in terms of understanding who is playing what, from where and for how long it has been quite interesting.
I don't use facebook myself as I find it too much in terms of maintaining any type of online presence however both YouTube and Soundcloud have great integration into all of the social media services like facebook, twitter and all of that mullarkey which means I don't have to do much in terms of trying to promote my music - if somebody finds it interesting or useful they will share that and if they don't, I don't lose any sleep over it as I'm not committing hours of my life trying to promote or market something, when really, I'd prefer to be either playing, writing or listening to music.
From the Google Analytics I can see when something gets posted on Facebook, Twitter, LinkedIn and in some cases who did the sharing. This was useful when I took out some online advertising last year as I could see how many people had came into my website from the Ad and could see that the Ad was actually worth the money I had paid (£150 for one month of banner ads on an online radio website in the UK specialising in the music on CD) - I sold enough CD's that month via the ad, that the exercise paid for itself and I was able to see that quite clearly. These were also physical CD sales from my website via paypal, so I get 100% of the revenue.
For my SoundCloud account, I have configured the ISRC codes and iTunes links on all tracks and on the set so it is easy for people on either SoundCloud or my website to buy tracks of the Album with the minimum of clicks. Again, I can see all of this from my Google Analytics account too. The biggest margin I make on my online CD tracks etc is via iTunes so this is the channel I have "promoted" by configuring this into my SoundCloud account however you can customise these links to go to your CD Baby account so that people can get to your commercial tracks via Soundcloud very quickly.
And lastly, a number of my tracks were included in a SoundCloud playlist before Christmas, which meant that they were played as part of a shared playlist for about two weeks. This essentially advertised my music to a wider audience than I would ever reach as I generally can't afford the time to do anything beyond my day job and uploading the odd track here or there when I get a chance. The number of "listens" to my VSL version of Bach's Little fugue (https://soundcloud.com/mcelvogue/bach-little-fugue?in=mcelvogue/sets/classical-copies) went from 40 to 400+ in about two weeks. I don't have anything commercial in this space to sell however if this had been any of your works, I'm sure there is potential sales that could have been made by doing very little other than uploading the tracks and linking them to where they can be bought.
The music I would be selling commercially has a much smaller market than the classical, baroque or any other market for that matter and I don't have the time or inclination to do all the self-promotion stuff that most other musicians tend to get into (competing for how many friends they have on Facebook, how many likes they get etc - that's all a great for stroking the ego but if you're intending to make a living at the music stuff, what is important is - in my opinion - is how many people actually end up buying anything on offer which is a totally different challenge). I know that the facebook stuff does work for some artists, however in order to get people to firstly listen to your music, it needs to be out there and available for people to hear. The market is absolutely flooded with all manner of tosh as Hetoreyn stated and I think it is an extremely difficult task to stand out. Personally, I think that unless you have the weight of a big record company who is willing to take out all of the sponsored links, online promotions, media advertising etc it's simply not possible to stand out other than to accept that the market is relatively small and the corresponding revenue that is available is minimal. That's why I think it is so important to make the most of what revenue is available.
Most other music genres would use touring and performances to spread the word, generate a buzz, get people talking etc which is a much more direct and human way to whip up some interest in this genre and get people buying the music/merch etc. Sadly, these options are probably off the table if the product cannot be toured or performed in the same way which only really leaves the other revenue generating avenues which need to be exploited to their maximium (royalties, downloads, online sales, licensing). To me, this means maximising every commercial opportunity possible whilst minimising the amount of time spent doing anything else not music related. This is why the Soundcloud linked into my website works for me. I only have to update the sets and tracks on SoundCloud and my website is immediately in synch. I don't have to do an editing or anything else. I also switched to a wordpress-based template website which means I no longer have to get into the coding of HTML, Javascript or anything like that. I can update the site very quickly, from anywhere, using just basic word-processing skills.
Another thing I found is that I am also interested in photography and used to do quite a bit of this a number of years ago, both personally and professionally. By putting some of my photographic stuff online, people who would otherwise go to my website, find nothing of interest (musically) and then return to whatever they were doing in first place, start to spend more time on site and funnily the sales went up. I think it is akin to having a retail outlet in real life. If you walk into a shop and there is only one or two products on the shelf (and nothing grabs your interest or imagination) you leave and go to the next shop. If you can find a way to keep people on your site, even if the products or information is not directly related to the products you are selling, it engages people and they are more likely to take a second listen or look at what you're selling. I'm not sure if this is something relevant to you or not however I do recall seeing that you also direct and make films. I'm sure it couldn't do any harm to have some of these on your site (served from YouTube).
Anyway, that's my rant over with but I thought it might help in terms of offering up my experience with the whole internet mess thing that we now seem to have to contend with. Apologies for wandering all over the place with this post.
Tom