Sia has great a development team and an ambitious roadmap.  They have working technology that leads to really cheap storage and they have become partnered with different frameworks to allow Sia use as cloud storage option.

Of course you should diversify your decentralized storage investments.  Storj is also doing pretty good and there are a lot of new contenders.
I am really excited about Oyster because they are monetizing decentralized storage in an interesting way which lets website owners monetize visits without needing ads.