In his answer to What's the difference between the Nashville Number system and a Roman Numeral System?, Dom states that "Roman Numeral Analysis as stated is used mainly in analysis while the Nashville number system is more for practical purposes." He goes on to say that the NNS makes inversions a bit more intuitive (5/7 for a first-inversion V chord, instead of V6), but that chromatic chords are easier in Roman numerals.
Based on the above information, the NNS would be best suited for completely diatonic music, which is relatively uncommon in popular music (the repertoire for which the NNS was devised). Furthermore, it seems odd that a main selling point is inversions, when figured bass has worked just fine for centuries.
So in what context(s) would one prefer the NNS over Roman numerals?