for trading - alternative altcoins, because i think will be max profit. For holding - bitcoin or etherium.The choice is yours. Good luck
There are also other altcoins worth holding, not just ether, I believe some altcoins will become very expensive in next few years.For trading it doesn't matter which one, as long as you follow market.
I wish I had bought Altcoin instead of Bitcoin when watching recent XRP and other Altcoin prices rise 
Wait for dip and buy them 