Ethereum is very solid now. It processes over 500k transactions per day and the fees went down a lot after the Byzantium upgrade. The pool of pending transactions dropped down to 80 despite all time high of 546k transactions in 24h. Average transaction fee: BTC $3, ETH $0.17
So many projects use it. For example, there just was a huge Eth hackaton with over 300 developers:
I'd say that today, the number 1 most useful platform is Ethereum. It is terribly underpriced compared to BTC (1 BTC = 20 ETH) despite being so many times more useful.
BTC is pure speculation, ETH is the real thing.