I think Shift for a few reasons:

1. Niche product that might be actually be more useful than you think. Yes, right now there are decentralized apps interacting with cryptocurrency networks (ex: Edgeless on Ethereum), but the website itself is not decentralized. A decentralized web platform will allow developers to easily decentralize entire stack (web server, webapp logic, etc.).
2. It is kind of a first mover. Its closest competitor, Substratum, doesn't have a product out yet is trading at ~3x the market cap of Shift ($75 MM vs. $27MM). Shift has much more progress thoughI think the cause of this imbalance can be attributed to Shift's lack of marketing, low communication, and a semi-anonymous/mysterious team. But it looks like they are ramping up marketing plans in the next months, and will actually launch Shift's Phantom dApp in production in the next months as well (and the new site will be running on Shift). If marketing/launch plans are successful, I fully expect Shift to go to at least $100MM market cap just on this alone.
3. I think the DPOS consensus algorithm (delegated proof-of-stake) will dominate in the future, due to problems of hashpower centralization and energy use during mining. It has seen great use, since currencies like ARK, Lisk, EOS, Rise have all adopted it from the original implementation of DPOS in Bitshares (and all of these DPOS coins have done well this year). Also, Shift is the cheapest in terms of market cap (Shift - $27MM, ARK - $380MM, Lisk - $900MM, EOS - $2B, Rise - $37MM). Yes, I know there are other, lower market cap DPOS coins. But I have looked into them and didn't really find any compelling one, that's also traded on a major exchange (Shift is on Bittrex, at least).

This is my personal analysis - please do your own DD before investing. If you want to be less risky, I suggest investing into bigger cap coins (my other recommendation, if you're looking for a different DPOS coin, is ARK).