digital pianos v acoustic pianos

The Differences
Digital pianos are electronic instruments that reproduce piano sounds. Unlike acoustic pianos, they have no hammers, no strings and no soundboard to produce the sound you hear. Instead, they have electronic sound chips and speakers.

Digital Advantages
Digital pianos usually have a variety of features that make them an attractive alternative to an acoustic piano.  Some of these features are as follows:

Different types of piano sounds
Other keyboard sounds like harpsichord, organ, etc.
Other instrument sounds like strings, woodwind, percussion etc.
Built-in rhythms to accompany your playing
The ability to record your performance
The ability to interact with other electronic music devices (MIDI)
Never requires to be tuned
Headphones to practice in private or late at night without disturbing anyone
Easier portability and less space required
Unaffected by changing room temperatures

Acoustic Advantages

Even with today's sampling technology individual notes may be quite accurately reproduced, but the tone of notes sounding together, as in an acoustic piano - with complex harmonics mixing and resonating against a flexible wooden soundboard - cannot be matched.
Something else to consider is that an acoustic piano will hold its value much better than a digital. An acoustic piano can last 100 years, while a digital may be obsolete in 5 years.