To be frank, there is nothing to compare here, Bitcoin is the king and the top cryptocurrency not just because it is the first but because it offers the most decentralized blockchain, secure and reliable, and because of this reliability made a lot of people to value it more than any other crypto; so yes it is the best.
On the part of Ethereum, Ethereum is good as well, in fact it is the most valuable altcoin but I don't think it can be compared to Bitcoin, rather I will say Ethereum knows it's place in the crypto space and thus keeping to it. I have never seen any sort of competition between Ethereum and Bitcoin, in fact no coin is competing with Bitcoin.
In addition, when you see news of most big cooperations buying cryptocurrency, which coin do they mostly buy? Bitcoin, because they know it can be trusted while on the other hand, when you see most cooperation looking for a blockchain to work on, they mostly go for Ethereum because it offers the best smart contracts; so you can see there is no competition between them, so no need for comparison.
Thus, you can invest in both or any of them depending on your capital.