Where Bitcoin is a currency like your dollars or Yens, that you can use to trade and buy commodities in the digital world, but Ethereum is a platform. Ether is the currency which fuels the Ethereum platform, while Ethereum platform is a decentralized stage, powered by blockchain technology, that enables developers and tech entrepreneurs to develop their applications and benefit from the robust security features and powerful technology of blockchain.
Ethereum might be less in value than Bitcoin right now, but the stability and future of Ethereum is brighter because of it being an entire platform, and not just a coin or currency. And the biggest benefit of an application on Ethereum platform is zero downtime.
The applications that are developed on the Ethereum platform, can be funded by public, using ICOs (Initial Coin Offering), in which the companies can release their own tokens, which can be purchased using Ethereum-coin as the currency, thereby energizing the company. Bitcoin has no platform on which developers can develop applications, while Ethereum provides so, which also makes it a diverse player in the market.
In fact, both digital assets will likely hold a place in our future economy, bitcoin as a monetary system and ethereum as a platform for building the next version of the internet. If bitcoin is digital gold then ethereum should be considered digital crude oil, a powerful source of energy for the decentralized apps of the future.”.
https://www.crypto-news.net/ethereum-bitcoins-biggest-rival/