Visually I think Kakarot has the edge because of the particle effects and the animation in the cutscenes. Even if the characters do look a little off. Besides Battle of Z (and Jump Force if you count it), Xenoverse has got to be one of the most visually unappealing Dragon Ball games.
This is another unpopular opinion, but the real time combat Xenoverse has takes away the wow factor Dragon Ball puts into the transformations and attacks. You get God Punisher or Big Bang Kamehameha in this game and they basically hit like wet noodles compared to the sheer amount of hurt and destruction they laid in the anime and in other video games.
I think having destructive finishes like Kakarot and FighterZ have does it a little bit more justice, even though Kakarot only has two (for Spirit Bombs and for Kamehamehas). I also think changing around the perspectives in the attacks when the player hits the surge mode was also a smart idea and so was the powering up thing.
I see a lot of people trying to mod stuff like this into Xenoverse 2 so it can't be too unpopular. But if you ask me, flashy attacks and explosions and transformations are a part of dragon ball, and shonen anime in general. They don't have to be long and dragging like NUNS, but they at least need to look good.
On to gameplay, I don't like how either of them just bloat the enemies with health. I think Kakarot has the edge here, too, but barely. I don't like how when the boss powers up you have to stop your combo while his guard meter fills back up. I'd say Kakarot did a good job at the boss fights however. That and the fact that there are only two types of destructive finishes (dome shaped explosion and kamehameha flying out into space) are my only issues
My biggest problems with xenoverse is the fact that it doesn't have its own tabs for transformations and the way the roster is. It needs to be more like NUNS4. The way it is now, you've got SSG Goku and SSB Goku in different slots. It's a total waste and made to make the roster bigger than it actually seems.
You've also got the braindead A.I who make the PQs more frustrating than they have to be. And the instances where the boss keeps talking, trying to prep for a cutscene, and you can't do any damage but he can still hurt you and the ally.Kakarot's ally AIs are better, but that may be because I can control their attacks and the fact that they don't die. Although I think they missed an opportunity to make team attacks with the Z combos.
Story wise, Xenoverse takes the cake. I'm still angry that DBZ K wasn't about Dragon Ball from the start. Better late than never though. Another thing that bothers me is how this was supposed to include "stories not seen in the original manga" but the most interesting thing was beastmen being a drug fad.
They had plenty of stories to include, like Goku's adventures dead (twice) or his time in Yardrat. Then they dropped the ball with the BoG and RoF DLCs. I still have no idea what the deal with that RoF DLC was. Nothing like the movie at all. Trunks' story was a step in the right direction though and so is the upcoming Dragon Ball story.
Xenoverse actually had some interesting concepts so it wins, but I don't like how, after like 7 years, the best they can do is "this character is stuck in some random arc...and he's purple! beat him up!" Budokai Tenkaichi 2 had better what-if stories. Hell, this throwaway NPC in Xenoverse 2 is doing better missions than us. I also wish we had what-if characters like Heroes.
Basically if I just wanted to hop back into one of the games and play through a random mission I'd choose Kakarot 9 times out of 10. Everything but the story is just a little more enjoyable.