No API changes to either of those methods in 2.0.
the pathToTestFile property is for doing automated testing or replicating an issue with the complete continuous listening context, and was introduced in mid-2013 and continues to be available: https://www.politepix.com/2013/08/26/openears-1-5/. You may have seen me recently mention it in a discussion about how to replicate a recognition issue in 2.0, but the discussion wasn’t about pathToTestFile itself or changes to it.
runRecognitionOnWavFileAtPath:usingLanguageModelAtPath:dictionaryAtPath:acousticModelAtPath:languageModelIsJSGF: is a convenience method for running recognition once on a complete WAV (although I don’t really recommend using it in a UI – it was made available as an early test method and has been kept around as a way of seeing whether the continuous driver is introducing issues since its results can be compared with pathToTestFile which uses the driver, since it doesn’t use the driver) and has been there since 2012 and continues to be available.
They are both intended as testing tools, and as a testing tool pathToTestFile is greatly preferred since it tests the entire continuous listening context. If you are using either for something else, it makes sense to just use the one which you find simpler to use or is more semantically related to your task (that would seem to be runRecognitionOnWavFileAtPath:usingLanguageModelAtPath:dictionaryAtPath:acousticModelAtPath:languageModelIsJSGF:).