behavior wise it is impossible to say which can be domesticated as Upper pointed out. We can't measure how aggressive a fossil was. What really determines what is domesticated is what can be domesticated, llama are terrible pack animals but they were the only thing available to the Inca, so that is what they used. But the big factors like temperament, breeding behavior, and other behavior leave no fossil evidence so we have no idea.
Now assuming you can just say yout dinosaur has the right temperament, we can say anatomically which would be more useful if domesticated.
There are some key traits you want in a pack/riding animal.
Herbivores generalist (or possibly omnivores like dogs), it needs to be easy to feed, you want to be able to feed it a wide variety of plant fodder otherwise it is useless for traveling. Grazers for preference, since grass is a lot easier to harvest.
breed quickly, if it takes too long to breed it is all but impossible to domesticate. You want many generations per generation of human, that rules out some of the larger sauropods.
Quadrupedal, while it is true some bipedal animals can be ridden, they can not carry people long distances and are useless for carrying cargo. You have to be really careful about distributing weight on a biped, quadruped animals are more forgiving. You also have the issue the only place you can sit or place cargo on a biped is right over the hips.
Herding, this is seen in every domesticated animal, sociality is a basic need for domesticated animals. It makes penning, breeding, and working with possible.
This leaves you with only a few groups, ceratopsians, large ornithopods (smaller ones are often bipedal), or small sauropods. Although larger ankylosaurs might be an option, we don't know if they are social.
lets look at each of them
Ceratopsians probably give you the greatest range of sizes, and they could be fitted with a saddle easily enough. Roughage diet which is good. No real downside.
Ornithischians appear to have spines along the back, so making a saddle would be tricky, on the other hand we know some are great distance travelers with migratory distances as high as any cursorial animals alive. There are many variations and plenty of grazers among them to pick from. good pack animal (sling packs), but tricky to ride.
Small sauropods are still huge and would be great for large loads especially if you stick to good roads. Big does make for slow breeding and training, they are also harder to feed since they are browsers. Probably not a good choice for anyone but royalty that can afford to feed them.
Ankylosaurus are slow but strong. They are bulk feeders meaning you can feed them damn near anything, plus the spines are mostly horizontal which makes it easy to pull a plow or wagon (they literally have built in yolks). Not great for riding though, very wide, you could build a chair like saddle however. Possibly solitary which is bad, but this is disputed and many not be universal in the group.
So you have your pick of those four groups.