I'll just start by saying I like both, but they are both very different send-ups to popular franchises that have the same exact audiences.
The Orville is Seth McFarlane's love letter/pretty much a ripoff I'm surprised isn't getting him sued. The Orville is also suffering from a standard disconnect between audiences and critics. Rotten Tomatoes currently has the critic score at 20% and the audience score at 90%.
Critics of "The Orville" have pointed out how similar it is to Star Trek:TNG, but have also pointed out how the jokes aren't really a cheap gag every half minute like Family Guy is, which is how this show was advertised. The best comment I heard about this show from a fan is that it's like Stargate SG-1, a serious show with witty banter. Except it's done in Seth McFarlane style.
Star Trek: Discovery is also pretty sweet, but it's a different style. It's trying to combine the seriousness and ongoing, multi-episode plot of DS9, with the actiony bits of the J.J. Abrahms movies. It's doing it better than Abrahms. That's all I'm going to say. Now is a great time to be a Trek fan.