I believe that neutrality and realism are one in the same when it comes to the goals of audio components and the reproduction of music. However, many (maybe all) companies that use such adjectives to describe their equipment do so only for marketing purposes. Understandably, they're in business to make a profit. Some manufacturers, such as Levinson/Madrigal, produce equipment that is lifeless and unemotional, painting a "two dimensional" picture and robbing the music of microdynamics and pace. The audiophile press has praised the "neutrality" and "accuracy" of such gear. Others companies, like Krell, tout "authenticity" and "realism," but have a highly polished, chrome plated, "larger than life" sound that is great for a brief audition and a quick sale but eventually proves to be too bright, too brash and fatiguing. Many users and purveyors of tubed gear assert a claim of "musicality," which I gather is supposed to a higher plane of both neutrality and realism. Unfortunately, tubed gear often produces a warm, euphonic and overly romantic sound that exaggerates the midband and smears the timing of music. I'm sure others will disagree with or be insulted by my opinions and examples, but ultimately, it comes down to what flavor of coloration you prefer.
neutrality vs. realism
What is actually the final goal of high-end audio: to reproduce recorded music as neutral as possible or to give the highest possible level of realism? For some manufacturers (like Spectral and Madrigal) it is the ultimate goal regarding their amplifiers, to sound like no amplifier at all. There is less coloration, less "house sound", more "truthfulness". I think this is a good basic consideration, but it must not derive the sound of it's musicality. Those amplifiers are generally sounding lifeless! Don't get me wrong, this is not about the tubes vs. solid state controverse at all, because I think that solid state amplifiers are able to give a high level of musicality without sacrificing neutrality (Boulder, FM Acoustics). What seems perfect on paper is not always the way to go: "neutrality" and "perfect measurements" are not the synonyms for musicality and realism.