A poll conducted by GSMArena suggests that Android Auto is used by 50.1% of car owners, while only 17.4% use Apple CarPlay. No insight into the “I use my phone with a holder” camp is given, as they could be Android or iPhone users.
Other poll results are below:
Does “Android Automotive” count as “Android Auto” or “My car’s built-in infotainment”?
Edit: For those that don’t know, Volvo and Polestar (maybe others), use Android for the native infotainment. This is called “Android Automotive” to distinguish it from the version powered by your phone, called “Android Auto”.