Sia is the only one that is actually relatively decentralized, and distributed through fairly PoW. The other two are ICO's, and aren't worth dealing with for that reason.
I would add Oyster Pear which is quite similiar to Siacoin with two advantages. For one, you can currently use it for free. Everything you upload now will be free for one year, then you need to pay 1 PRL for 64 GB storage. As soon it is pegged to that storage you should also see its price jump to 5-10 usd. And then there is the 2nd part of this project that enables web hosts to monetize their sites using the computing power of visitors to mine PRL instead displaying ads.