Well if i were you i would not put all of my money into only one coin. Ethereum will be good you are right but you can make much profit if you put your split your investments in couple of high potential coins.
My portfolio composition consists only maximum of two altcoins only. But when I'm sure that my coins are bullish and uptrend I usually put my money on single coins only. Before doing this you must follow strictly the trading plan (entry and exit). This strategy is works perfectly on bullish market. I don't invest when the market is bearish. I just hold and watch only until the market correction stop.