Oh I love thinking about this sort of thing; I have tons.
What was it Christopher said about David Mack, that he had a tendency to never let his characters off the hook, to make them make difficult decisions and then really experience the consequences? Something like that. That's a much better way of phrasing it than the usual "HE KILLS PEOPLE A LOT!" stuff. That's true, but it's not just random or gratuitous. In most Trek, if someone decides to sacrifice themselves to save everyone else, they probably make it somehow. In a Mack story, if they decide to do that, they're gonna die.
Peter David, even before New Frontier, was definitely the funniest Trek author, though he too had a tendency to put characters through unusual amounts of hell.
Christopher's novels almost always feature people working through deep emotional problems with long-form psychology-literate introspection and logic.
David R. George III often will focus his novels on unlikely thematic connections between disparate stories, most especially with Twilight having every story be about loneliness, but also Spock & Sisko's almost unconnected stories in Rough Beasts, McCoy's two distinct lives in Crucible, Demora's story and its recipient's implied story in his short story in Tales From The Captain's Table, etc.
You don't find too many people being violent, mean, or depressed in a KRAD book, unless it's the Mirror Universe.
Diane Carey's nautical lore has been mentioned.
Martin, writing by himself, tends to oversimplify emotional conflicts and get lost up his ass in unnecessary continuity bitchfixes.
Ward & Dilmore almost always spend the first quarter to third of a novel just letting every character monologue about everything that's happened to them lately; it feels to me like they just want to spend some time hanging out with the characters before making them do anything. Depending on my patience level, it's either endearing or really frustrating.
Margaret Wander Bonanno can never quite seem to write a plot worthy of her characters and emotionally genuine writing style.
Kirsten Beyer is awesome.
Una McCormack likes to hint at her characters' motivations without fully explaining them, which is thematically rather brilliant given how much she writes about Cardassia. Or maybe I'm getting cause and effect backwards there.
Whatever the weirdest thing you've read lately is, Ilsa J. Bick is way more fucked up. This is true even though she's written very few Trek tales.
L. A. Graf's books are going to be about the lower decks characters, especially Chekov.
There, how's that?
