For ethreum is undoubtedly because ethreum is a long-standing coin in the market, and we can see now the price movement is getting better and this will break through the highs in 2017, if you want to make an investment now I think it can still hold the coin because the price will definitely go up again in the near future.
ETH is always next to bitcoin's success, it will never surpass bitcoin but it will always follow its success. Did we expect ETH to reached $1000 this easy? No, we didn't expect it, but look where is ETH now, so we should not doubt it, invest as much as we can especially if we are looking to hold longer.
However, if you want to buy cheap, best way is to wait for the price to dip.