ethereum
- Two chains, confusing to almost all noobs (potentially more chains over time)
- The HF chain may switch to PoS soon, no mining needed (questionable security)
- Unclear when new coins will stop being produced, no true finite coin cap AFAIK (fiat 3.0)
- PoS system gives power to large holders, these holders won't be challenged by miners
- Vitalik and company can print as much as eth as they want until satiated, switch to PoS, own the HF'ed chain until end of time... and if a thief comes in and steal that majority stake, what then? At least in btc I can't really fathom miners like bitfury losing control of their own equipment to hackers.
- Objective of ethereum not clear and perhaps not useful for 99.9999% of people
bitcoin
- Nothing technical about the coin has fundamentally changed since the beginning other than some functions and bug fixes
- Has finite cap with predictable inflation
- Relatively easy to use and easy to understand; clear goals for its existence with already existing use cases (store of value, fight against inflation, international/borderless remittance, easier form of payment for many, uncensored record of transactions)
- May get smart contract abilities via sidechains, leveraging its unbroken secuirty (miners) without jeopardizing the main chain (you could just HF the sidechains)
- Only issue is tx/s. I expect this to be solved in due time. For now transactions are not free and will cost you a few cents. That's fine since we're not yet at an economy where millions of folks are buying Starbucks with BTC.
- No one has total control over btc. But core and the miners currently hold the keys. In due time this will change as pressure to increase functionality of BTC adds up.