It's like this:
Move has all the sensors that a Wii Remote with a WiiMotion addon has.
In practice, that makes Move already more accurate, because even of the brand new Wii releases hardly any game supports WiiMotion , simply because it's an optional addon that most Wii owners don't own, and requiring WiiMotion would reduce the number of potential customers for your game a lot. The gyroscope that makes WiiMotion more accurate is however included in every Move controller, so there's no reason for developers not to use it.
In addition to the sensors found in the Wii Remote and the WiiMotion , the Move furthermore has a magnetic field sensor builtin, which further improves the accuracy. So even the Move controller alone is more accurate than a Wii Remote/WiiMotion combination.
But Move of course furthermore has the glowing bulb and the Playstation Eye, which are used for calculating the exact 3D position of the controller in the room, which is something the Wii doesn't support at all.
