I like Steem especially because it's already useful - it doesn't need to find a killer app. If it can just fix this website and curb abuse (which is a tall order), then it could easily become one of the biggest cryptocurrencies out there. Ethereum has a tall order in terms of getting more useful applications on its platform, but I think it will come especially as developers have every incentive to get their stuff together now that cryptocurrencies took off in 2017.