In my opinion both are good options to invest. Why not 50% Ethereum and 50% Dash?
Because Eth is the better bet? It's more stable, less chance of losing a good portion of your investment.
Ethereum is very stable. I think that it will be very hard for ETH to lose a good amount of his money in price. There are also now more coins that are based on ETH.
So i would go for ETH surely just because there are many people supporting it.