Just attended a lecture by Shakespeare actor/director/professor Tim Hardy (great), and he mentioned something about how words sound creating a particular effect. He mentioned doing a comedy where for some reason the actor had to say (as the punchline of a joke) the names of two New England states, Vermont and New Hampshire. One time he said it backwards, first New Hampshire, and then Vermont, and it didn't get much of a laugh. The next performance he got it right, Vermont then New Hampshire, and got a huge laugh. They were puzzling over the difference in response, because it didn't matter to the joke itself which came first.
He mentioned this to the comic playwright Neil Simon, who said immediately, "You can't end with Vermont, because Vermont isn't funny." He didn't mean the state (which isn't more or less funny), but rather the sound. "Hampshire" is funny, see, because of that P in the middle.
Mr. Simon averred that propulsive letters (P, B, and F), the ones that SPIT, are inherently funny, and that an ending word with one of those will cause more laughter. (Also said that "L" was NOT a funny sound, which is funny, because, you know, "laugh.")
This goes along with my thought that ending words in sentences and especially paragraphs are either "upbeat" or "downbeat," and that an upbeat ending ("Okay?") calls for a downbeat ending ("Yeah, okay."). The sound of words-- even in written prose!-- causes an emotional and mental effect on the listener/reader, and if we want to have "natural" sounding prose and especially dialogue, we should be aware of that (unless we do it naturally, in which case we shouldn't mess with it... but if we're ever accused of having "wooden or stilted" prose, we're probably not doing this naturally).
Sound matters, even in written prose.... and it matters even more with sophisticated readers, and editors and agents (and bookbuyers) are usually sophisticated readers!