I hope I'm not becoming a conservative reactionary(!), but I basically agree with William. Atonality/pantonality tends to be emotionally monochrome. It’s great for portraying paranoia, neurosis & the dark side, but not so good with other emotions. Schoenberg’s atonal Holocaust document "A Survivor From Warsaw" rightly shocks & horrifies me, but his atonal opera-buffo comedy "Von Heute auf Morgen" doesn’t make me smile at all. Of course the "vulgar" atonality found in film music corroborates this - it's used for tension, disaster, horror, but not for, say, romantic bedroom scenes. Could atonality be used to depict ecstatic happiness, an atonal "Gloria In Excelsis Deo"? If it can, I haven't heard the piece that does this - yet.
Classical tonality is a multi-dimensional universe of 168 (24 times 7) notes. In this universe "A" as the 3rd of F major is completely different from "A" as the key note of A major, & any good musician knows how to play with these multiple meanings. Schoenberg flattens it down to a single 12-note mode, a single chromatic raag, in a single emotional plane. All that multi-dimensional play (or ‘modulation’) is lost. There is a kind of play between serial transpositions, retrogrades & inversions & so on, but it doesn't begin to equal what's been discarded. Imagine a great Indian musician, say Hariprasad Chaurasia, living his entire life performing in a single raag, with a single emotional association, a single time of day. That’s what serialism feels like to me.
I'm not saying serial music is rubbish, because there are masterpieces of that single atonal raag: Pierrot Lunaire, the String Trio, Webern Opus 5 etc.
Laters
Guy