ETH keeps the good promise in 2017, and I believe ETH will do it again in 2018.. I'm very confident that ETH is better than XRP in most thing..
You can always invest in XRP too, but I think, XRP price is very volatile these days ~
I think he can divide his money to ethereum for 60% and 40% for ripple. I think ethereum will have the best time in 2018 and the price will increase highly and this will happen too with ripple. while ripple still cheap, I think he can buy a lot of ripple and only hold the amount until the price increases. and now, ethereum start to increase more and it is happening on every exchanges and I hope the price will break more than 0.1 btc soon.