I've been a user of SoundCloud for over 8 years, and now I want nothing to do with the site.
Like Newgrounds, SoundCloud is the site that allows you to upload your own music and share it with others-- but differences lie within its community. Unlike Newgrounds, there are no forums on SoundCloud, so there is absolutely no form of communication on the site if you're looking for advise to improve on your music skills. You might be lucky enough to get a response if you comment on a song.
I'm also not a fan of SoundCloud's premium membership. Sure, you need to help pay for the site somehow, but this limits the user's creativity by only having n minutes before they can't upload any more tracks. It especially hurts low-/no-budget creators like myself. Newgrounds has a premium membership itself, but at least it's not required if the user wants to have the best musical experience on the site. Everybody has an equal chance of getting their music out there, without the need to pay for more attention.
Speaking of attention, let's talk about celebrities and record labels on SoundCloud.
Imagine being on the same playing field as professional musicians, who already have the money, resources, and the people to make an instant hit. I'm sure everybody knows about Drake, Dillon Francis, Armin van Buuren, etc. They are on SoundCloud also, and they absolutely overshadow the tens of thousands of creators on the site who try to make it big and fail.
On Newgrounds, I have 65 followers. On SoundCloud, I have 146.
On Newgrounds, I already have two frontpaged songs, each with over two thousands views. On SoundCloud, I struggle to reach a hundred views on most of my tracks, yet the top songs are covers. On Newgrounds, my best songs are originals.
SoundCloud fails to help me as a creator, and that's why I'm done with it.