That's actually a good question. For example, the technology is still currently at a level where the user can still cleary tell that it's a chatbot, but now with a face. Does this make their experience better? Or does it add a weird level of uncaninness to the experience?
It'll depend on the use case- but with customers that are using it today we're seeing higher engagement and satisfaction rates. It's a different interface to communicate that is more natural to humans (our bullish opinion).
I don't think the level of fidelity actually matters as much as authority or ability. What can the agent do that isn't accomplished by, for example, a landing page or an FAQ page? I've never encountered a (text) chatbot that did anything useful for me as a consumer, whether for sales or support.