As to whether or not a digital is better than an acoustic depends largely on what you want from your instrument. At this point, bear in mind that a digital piano is an emulation of an acoustic and, as such, due to limitations on current technology, it also has limitations in how close it can get to entirely replicating the nuances and fullness of a real acoustic or grand piano. Although there have been great strides in the development of keyboard units and hammer action, even to the point of using real wooden keys or real grand piano keys as seen in some Kawai digitals, they still don't quite capture the realness or interaction that can be enjoyed at an acoustic.
Does that make them useless or frauds at best? Hardly! Digital pianos are certainly more versatile and because they are designed with the intention of not needing tuning, they can be used in venues or settings that would not suit acoustics. Acoustics are temperamental instruments and hate large temperature and humidity variances in their environment. Moving them can cause immediate detuning and their weight makes them less than mobile. Their awkward size and dimensions make them unconsiderable as a choice of instrument for those with limited space or living in apartments. The digitals however can overcome all of these challenges and that is what makes them viable and worthwhile - no matter what the local piano tuner tells you!
While digital pianos are not exact replicas of their acoustic counterparts and can not, as yet, completely provide an acoustic piano experience, their ever increasing popularity show that they are fulfilling a need in the music world.