Technically and in terms of craftsmanship, The Orville is the better of the two shows.
1: Story cohesion.
“Show it don’t tell it” is a well known term for what a TV show is supposed to achieve. If you look at the two shows there’s a stark difference in terms of the quality of writing. Episodes of The Orville make sense and are true to the in-show universe. The show manages to tell a story without a lot of post-episode speculation and filling in the blanks.
Star Trek Discovery otoh? Not so much. After each episode of STD, the forums light up with fans trying to fill in gaps in the storytelling, and figure out stuff that didn’t make sense: Why did Burnham break into the lab? Why would they use a breath-sensing lock? Why would Burnham suddenly commit mutiny?
This is indicative of a poorly written show, where the audience is left wondering about this stuff, and filling in blanks that shouldn’t have been there. The set and setting and characters and their motivations are either not explained, or poorly sketched out.
2: Characters.
This is another point where STD really drops the ball. The Orville isn’t pretending to have super-deep and complex characters, but even after just 2-3 episodes I care about these characters and what happens to them. How about the characters on STD? After 3 episodes I still don’t give a toss about any of them, with perhaps Cpt. Lorca being the only bright spot or exception.
Burnham is supposed to be the main character, but she could get thrown out of an airlock in the next episode, and I honestly wouldn’t care. In fact, I doubt that even people who LIKE to watch STD (or want to like it) would be very upset if Burnham got spaced.
Now some might say that you can’t compare the characters on the two shows, so fine: Let’s compare STD with another character driven sci-fi show with complex characters: Babylon 5. B5 had bad guys you couldn’t help but cheer for like Londo. Truly tragic figures like G’Kar. Badass bad guys like Bester or Morden and badass good guys like Ivanovich or the head of security.
STD got.... Well, there’s Lorca and that’s pretty much it. None of the other characters are terribly interesting or noteworthy. It’s just a crew full of forgettable characters on a show that tries too hard to be BSG with a thin Trek veneer.
EDIT: BTW, Criticism of STD often gets handwaved away with ad hominems about Trekkies who just can’t adjust, but personally I’m pretty far from a “OMG! Gene’s vision!” Kinda Trekkie.
I loved The Expanse and don’t have anything against gritty sci-fi. I don’t like poorly written, gritty sci-fi however, and that’s mainly where my beef with STD is.