Even a low quality real piano is better than the best digital I've played. You just can't learn to do certain things properly, such as pedalling, on a digital.
This is not true. (Have you ever played on a Chalen? Give me a Clavinova any time!

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The top range of digital pianos will always be superior to the lowest range of acoustic pianos.
In fact a top of range digital piano is preferable to an upright acoustic piano because it will simulate double escapement (which an upright does not have), will have a sostenuto pedal (which an upright does not have) and the left pedal will simulate a true una corda effect (which in an upright is simply a muffler)
A digital piano will also have many advantages over an acoustic piano:

1. It is never out of tune.
2. It will give a number of different tunings at the press of a button.
3. It will have recording facilities. This is particularly useful in the context of learning/teaching, since you can record the right hand on one track and play along the left hand. You can also change the tempo of the recording, so you can play it at different speeds.
4. You can practice with headphones.
5. You can transpose at the touch of a button.
6. This is the least important advantage for me personally, but some people love it: you can have all sorts of different sounds.
Of course if you are comparing a top range digital with a top range grand piano (Bosendorfer, Steinway, Fazioli), then obviously the top range acoustic is preferable.
Also the lowest range of digitals willsupport your opinion. However, have you ever played a Yamaha Grand touch series? It will blow your mind off.
But why choose? Get both! (I have both and use them for different purposes).
Best wishes,
Bernhard