Defenetly Ethereum or Zcash. Ethereum is safer but you'll not make the same amount of X. Ethereum this year will maybe even get over bitcoin, faster transaction, lower fees, almost accepted by all companies that accept bitcoins, but it is much more used then BTC in the ICOs. On the other hand, Zcash is one of the most underrated coin with medium market cap that will explode at any time. I expect it to go 5x-10x at least in the very near future