It's hard to tell because both of them are good for long term investment and if you want to compare coin, look for another. You should know that these two coins are really made to serve as an alternative to bitcoin, and these coins has been in existence for a very long time, so you should know that they are both good for long term investment because they have future advantage over other coins because i think they have one of the most valuable real products.

Litecoin is meant to help in transaction because of its speed, and people have been using it for payment while Ethereum is built to support projects that are coming up, so you see that both of them have very promising future and I think you should invest in both.