Like apples to oranges? Yes, it is pretty much so. There are some key differences between Ethereum and Bitcoin which are important and they make these two completely different, still, there are many similarities, as well.
Ethereum is more than just a cryptocurrency. On its network it is possible to run applications and it has more than a few features, while Bitcoin is more oriented on storing value. Simply, the concept of Ethereum allows users to build new programs. With Ethereum there is more fluctuation of value. Ethereum is a platform that runs on its currency called ether. Since the beginning of its development, Ethereum swiftly reached the second place behind Bitcoin. Ethereum is decentralized which makes it safer from fraud or censorship. With Ethereum smart contracts there is more security and less additional costs.
Bitcoin is more adopted globally, since most of the retailers use Bitcoin, it is also recognized as a valid method of payments even in some physical stores. Bitcoin has greater value and bigger market cap. Simply, Bitcoin was the first cryptocurrency ever, followed by more than seven hundred alternative cryptocurrencies, popularly known as the altcoins.
Although Ethereum and Bitcoin run on the similar blockchain technology, block time of Bitcoin is about 10 minutes, while Ethereum block time is 10 to 12 seconds. Ethereum runs on the principle of so-called Ghost protocol and it has many advantages. The negative part is that Ethereum has more orphaned blocks. Besides that, there are some key differences regarding the technical aspects, such as Turing-code and the method of calculating computational power. With Ethereum every transaction is calculated based on its complexity, while with Bitcoin every transaction is regarded pretty much the same.
Development of Bitcoin and Ethereum was completely different. Most of the value stored in Bitcoin network is owned by the early miners. Ethereum was crowd-funded and there is estimation that miners will own for about 50% of Ethereum coins by the fifth year since the beginning.
But even so, both Bitcoin and Ethereum are very volatile, similar to every cryptocurrency on the market. They are both under the constant influence of the market. Although, supply and demand influence Bitcoin in more ways.