https://21.co/learn/#its-time-to-learn-bitcoinI'm spelling out the implications to get the discussion started. Notice the part in the intro that says:
By the end you should be equipped to navigate the more advanced Bitcoin Developer Documentation. And then you can go off and build smart contracts and autonomous corporations.
I like what 21 is doing and there definitely will be a lot of overlap between what Ethereum and Bitcoin can do. There are also many technical differences between ETH and BTC to ensure they both have unique advantages over the other in some areas.
The most obvious differences are network effect, blocksize limits and turing completeness