A lot of information has come out about the Quest 3 already.

Full color passthrough from cameras and a depth sensor (better than Quest Pro), 120Hz, slightly higher resolution than Quest 2, 40% smaller (whatever that means), Snapdragon XR2 Gen2 (they claim more than twice as fast as Quest 2), pancake lenses, controllers without the tracking rings, $500.

Compared to Apple's, the main downsides are lower resolution display (also not OLED), slower, no eye tracking.

Main advantages are price, support for games/controllers (you can still use hand tracking if you just want to watch movies), and no external battery pack.