Litecoin.
Although Bitcoin is making some steady growth out there, Litecoin is truly superior to it. Multiple Bitcoin-focused companies also started to accept Litecoin, besides the standard of Bitcoin only.
Litecoin is much faster, cheaper and has a far bigger growth potential. Litecoin is definitely my number 1 choice.
My number 2 would be Ethereum. Ethereum has a lot of potential, as there are a whole ton of ICOs being built on it. It's not going to fall any time soon, but I feel like Ethereum is more of a "stability coin" than a coin we should invest in, to make profit.
Bitcoin is another nice coin... It's going to stay worth a lot of money. Why? Because even when everyone realizes there are coins that are far more advanced than Bitcoin, people want Bitcoins, just because it's the original.
If Blockchain technology succeeds and I expect it will, as it has a lot of uses, Bitcoin will become a collector's item. Owning a Bitcoin would become very valuable.
As you see: I would take Litecoin.