Some people may tell you that Odyssey is just a reskin of Origins. There are some striking resemblences to between the two (ofcourse they were in development at the same time, Ubisoft not learning from their mistakes of the past). The combat is exactly the same but it has been streamlined for more coverage of playstyles.
Stealth, Ranged and Combat skill trees are still alive and kicking, but whereas Origins had you spec a whole array of different bows, all bow skills in Odyssey come under the same umbrella, meaning you can switch bows at will. Stealth is a little more interesting as the whole skill tree (particularly the DLC skill) are all superimposed by the animus and these skills are even made to hit harder than the generic normal assassinations of old.
Graphics are oddly more beautiful as well, especially on the PS4 Pro, they seem to have rendered the engine and smootged out most of Origins ugly edges (not that there were many to behgin with. Along with the new kind of Eagle Vision (in the form of Ikaros), you can see the beauty of the world alot easier. Looking at the Acropolis in all its splendor from the sky is particularly pleasing on the eye.
Unfortunately, it does suffer from the dreaded Ubisoft curse of copying a storyline of a predecessor. Origins saw you take down a cult more dangerous than the Roman Empire, where at the end both Aya and Bayek realised the need for an organisation looking to protect the innocent (The Order of the Assassins sprung from the bones of The Hidden Ones). Odyssey rips the story out of Origins in a weird copy/paste motiff. Cassandra/Alexios discover a cult who are trying to root out their family and fulfill a prophecy. It has the same mechanics. What is different is that you have the option to just take out the members needed to reveal the commander of the cult or take them all down at your leisure (which you'll have to do for the platinum).
Speaking of Platinums, this is also probably the easiest trophy list to accomplish since Ezios first outing in AC2. Nothing is really that challenging on the list, save for spending time revealing the cult and then hunting them down, which takes a considerable amount of time, but isn't actually difficult.