Which is better, BTC or ETH?

Could you please elaborate on the following question: "Which is a more superior choice, Bitcoin (BTC) or Ethereum (ETH)?" Could you break down the comparison based on factors like market capitalization, scalability, use cases, and potential future growth? Additionally, how do the transaction speeds and costs of both cryptocurrencies compare? Furthermore, could you discuss the community support and adoption levels of each, as well as the role they play in the overall cryptocurrency ecosystem? Thank you for your insights.