Web Crypto API - deriveKey vs. deriveBits?
It sounds like deriveKey is just a composition of deriveBits and importKey.  There is no cryptographic difference between ‘generating an AES256-CTR key’ and ‘generating 256 bits uniformly at random’—this is at most an API distinction.  Support for one or the other is inconsistent, apparently, even though they both appear in the W3C recommendation.  How to get around this in practice in a web application is a question for a forum on JavaScript coding, not crypto.se, however.