ETH has smart contracts and this is it's main advantage over bitcoin. This said, it's big question what will be the future of it if bitcoin introduces smart contracts in the future. At the moment i thing BTC is better investment.
BTC isn't turing complete, while ETH is. Term "turing complete" means it's possible to solve any logical problem with some programming language. So it's not possible to solve every problem with BTC, but with ETH it is. That's why BTC will never be even close to being as good as ethereum for making smart contracts.