I think many Apple users would be happy if only Siri could answer factual questions objectively and follow a conversation, being happy with a minimum of privacy collection like current location, name of spouse for messaging, etc.
While some may prefer a knowledge about you or you via people like you, as in, "Please recommend me a great movie", Siri is currently not in a stage where she may tell you stuff like "How do I mix a White Russian?" Google Assistant give me 6 steps with a photo and a follow up question "What about Screwdriver?" Siri gets utterly wrecked in the knowledge based questions.
I think the main problem is not privacy-related, but knowledge base-related. Google is building upon a fricking huge search engine via a knowledge graph and the sky is the limit for how well an AI can do. Apple is building on what, a shut down Ping social network, Apple Music listening habits, Wolfram Alpha hopes if all else fails, and a sparse Bing Search API if that failed too?