The Wii Motion Plus is capable of exactly the same "3D positional tracking". Heck, Tumble isn't even doing much that needs the "Plus" - in the end it's detecting where on the screen you are pointing at, motion towards/away from the camera (which is a very simple function of the Wii Remote), and then relational motions. It's really only one degree of relational motion that you need the "Motion Plus" for (but that one degree adds all the difference in simulating 1:1 motion).
If you ever want to see a good example of some of what the Wii Remote is capable of, check out Elebits (called Eledees in Europe). The game plays from a first-person view, with you shooting a beam that can drag things around the room. Once you've picked something up, you can drag it from side to side, raise it up or down, or push it further into the screen or pull it towards you (its controls feel rather similar to how Tumble works, though a little looser). And that's a Wii launch title, far removed with what the Motion Plus can do.
Really, a Wii Remote with Motion Plus is pretty much the same thing as a Move, they just work in slightly different ways, and each has their advantages. As I mentioned, the Move's big advantage is the camera - it can put an image of you in the game, with an object replacing the Move. Or record you doing different things. Or use a video image of the player to calibrate a game so it can do a good job of replicating 1:1 motion. All sorts of stuff. And of course the Move's ball can change color to alert the player for gameplay purposes, like how Heavy Rain turns it red when it's being used for gestures.
The Wii's main advantage is the Nunchuk has motion sensors in it - slightly less sensitive than the main Remote, and no gyroscope, but it can do some basic motion controls while the player is using its analogue stick. And the Remote has a d-pad on it, though it isn't really convenient to use unless you hold the remote on its side (which a number of games do use). And it's got a crappy speaker in the Remote, which adds to the immersion, since you hear sounds coming from exactly where your hand is.