Personally I think Bitcoin and Monero can co-exist without problems. There are strong use cases for both. I have some info about Monero here: https://anarkio.codeberg.page/monero/

Monero's main advantage is on-chain privacy by default (automatically hides addresses, amounts and TX history for all transactions, just click the "Send" button). Low fees (less than 1 cent) and 2 minute blocktimes (and relatively safe 0-conf) enable fast in-person transactions without a need for Layer 2. This benefits circular economies, such as a Monero-friendly taxi, convenience store or cafe. CPU mining makes mining more accessible and decentralized, and the tail emission (activated this year, included in the original 2014 code) means that miners will always have a block reward incentive, while keeping inflation under 1%/year.

I looked at ETH smart contracts around 2017 but didn't do anything since then. Smart contracts seem useful and many people like them. Dark.fi looks like a good, privacy-friendly and agorist smart contract platform (but not launched yet). I saw these two platforms for Bitcoin-based smart contracts: https://www.rsk.co/ and https://www.stacks.co/ but didn't try them yet.