They're both very good but the question you should ask is how much do you like wRPGs?
Origins takes influence from Witcher 3. Odyssey goes heavier into the RPG with more player choice and extra naval combat (if you liked Black Flag then Odyssey is an evolved form of the ship combat).
Personally I prefer Odyssey. Story is just as good and I like both settings, but Odyssey has taken the ideas in Origins and run with them.