It really depends on each listener's needs.
Apart from the orchestra, I know I tend to want to sing along full-out sporadically while listening. I notice I tend to feel most inspired to do so when singers like Warlow, Morris, or Ball step up to the plate. I tend to feel less enthusiastic when Byrne and Shimada come in, even though I think they are both fantastic as Fantine and Eponine, respectively.
So when I want to belt the sh*t out of "I Dreamed a Dream" or "On My Own," I press eject and put in Randy Graff of the original Broadway cast recording and either Frances Ruffelle or Linzi Hately for Eponine's 2nd act shout-fest. Those ladies can scream beautifully, and Frances, with a Rock-tinged flavor. Gotta love her.
When I feel like slitting my wrists (figuratively!!!), I put on Nagy Aniko's rendition from the original Hungarian cast recording. She's the most beautiful sounding wounded animal I've ever heard.
And when I am not interested in "singing along." I chuck it all to one side and slave away, creating my own orchestral tracks, to which I allow myself to sing to only if I am satisfied by how it turns out. Anal, I know.
And if that's the case, the neighborhood will strike contorted expressions for the next hour, or so, as I SING the crappola out of those songs, complete with machine-gun vibrato and scooping notes a-la-Lupone, leaving the barrio stunned, paralyzed, and trauuuuuuumatized.
Calm down. I kid.
Recreation of original John Cameron orchestration to "On My Own" by yours truly. Click player below to hear.