You can stream from Soundcloud as well as from Dropbox. I think that DB is a much more private re. means of sharing, as to which SC is a public sharing site, noting the "follow" and "search" functions available.
Are you sure that streaming is available in Dropbox?
When I go into my Dropbox folders on my own computer, clicking on a track will open up Media Player and play the track. But I am pretty sure that when you share a link to a dropbox folder, the recipient can view any photos or text file, but music files have to be downloaded individually and cannot be streamed; although I would be glad to learn that I am mistaken.
I am using the Samsung 4 of which the DB app allows me to stream. Keep in mind that the file needs to load first. BTW, I am extremely anti mp3, but I did load a few converted .wav to mp3 files up to my DB account and there was no load wait and it streamed very well. Not sure how well it works on other mobile phones?
For the record, I would never put all my recordings up on SC, unless it was my band and I was promoting the songs and or re-mixes many bands do. I prefer the privacy of DB over SC, but this is because I am dealing with who I recorded on a personal level and am not openly sharing as one can with followers using SC. I like both, but they are used for different purposes.