I'm not an audiophile in terms of music quality although I'll always spring for the highest quality version I can obtain when I have the choice but so long as that's not ~Top 3 on your list of important features of your musical source than I imagine Youtube might just be the best option for a given listener who has the capability to connect to the internet, has a speaker or musical setup to play music via the computer / internet / Youtube and the ability to connect Youtube / any internet audio source up to your daily musical needs (dock in bathroom while getting ready in the morning, AUX in car, headphones / dock at work, AUX in car, bluetooth boom box at the skatepark after work, dock to wind down to audio tapes while getting ready for bed).
Depending on what "general" field of music you tend to listen to the most Youtube is arguably the best source of music in the world if you have the capability and ability to use the internet and relay it to a speaker for yourself. The reason I say 'depending' is because when it comes to popular music, historical or forgotten music, less popular music, older artists, obscure artists, obscure songs, music from non-music releases (soundtracks, music embedded into tv or movies or games, live recordings, etc.) and that's just music -- not even getting into talk radio, podcasts, interviews, sports news, sports talk, political news, political talk, and the thousands if not millions of sub-categories and genres you could dig into for more entertainment.
Youtube is undoubtedly the best source for 99% of that type of material. Now the reason that I can't say 100% is because Soundcloud really does happen to have a large and disproportionately (oddly enough) relevant segment of what's going on in music today.
I think if you are the type of person who is really into EDM and going to festivals than Soundcloud might be a better all around music app for you -- depending on what you like to listen to them most.
For the vast majority (90%+) of my casual music listening I am listening to Soundcloud. A lot of the artists I listen to are outside of the US and their artist names and/or track names might be in a language I don't understand or even be represented by characters or kanji that I can't even start to interpret let alone type into a search bar.
From the outside looking in without any context or history with Soundcloud you may not see the appeal but if I sit here and try to rationalize things without injecting my own personal opinion I guess I'd just say that Soundcloud, over the last 5-7 years, has without a doubt been the largest source for individuals and labels / label A&Rs / music executives / taste makers / influential DJs / etc. to discover and enjoy new music by new artists in a very direct way. This has led directly to many of the artists we know and hear of today being a product of discovery via the Internet and Soundcloud.
When the Spotifys, Google Musics, Pandoras, and iTunes-types talk in private I always wonder how much they pay attention to the canyon between how successful Soundcloud is in so many needed / important / relevant criteria (in terms of metrics any competing music service would dream to hit) yet at the same time being a terrible failure in terms of earnings and as a picture of a company you'd want to emulate.
I wonder how much of the insanity of Soundcloud being broke yet making their biggest artists into millionaires factors into the other competing services going about business.
You obviously have to do lots of things wrong to be as big as known as Soundcloud is yet be broke.
Also, you obviously have to do lots of things right to be as big and as known as Soundcloud, be broke, and still be able to deliver that service that has kept so many faithful patrons and contributors coming back for more all these years.
It's like a train crash that you can't look away from. Sadly enough, I have lots of important memories and slices of entertainment on that train so there's more reasons than "I'm a morbid human" for watching it explode into a fiery ball of failures.