My choise is ETH. I think 2018 will be the year the Ethereum protocol shows its utility, proof of stake will start becoming a foundation in many blockchain infrastructures following Ethereum’s success.
MetaMask allows you all the same functions, features and ease of access from MEW, and it allows you to interact with Dapps and Smart Contracts, and all without the need to download the blockchain or install any software, you can just install it as a Google Chrome Extension. To see your tokens you need to add them manually like in MEW.
Most altcoins are not much more than just bitcoins, changing only 1-2 minor characteristics, for example, the speed of coin transaction in the network, the method of coin distribution, or the mining algorithm. Most of these coins do not live for a long time. The only exception is Litecoin, because it was created as one of the first altcoins. Compared to Bitcoin, litecoin has a different mining algorithm and a much larger number of coins.