As a owner of both, I'd say Naruto. (In my opinion)
To me, it seems that Burning Blood was made only to please the fans. I didn't really like the fighting style in the game. You can tell they didn't really put much work into it. And the standard price for it is 50 bucks. (No way in hell would I buy the game for that much)
But BB is on sale right now (On Steam at least) for 15 bucks. I'd still consider my options then. Only reason I have it is because I'm a major One Piece fan.
As for Naruto, it's pretty much said by most players of the Bandai Namco games that it's the best anime-fighting game they have. Surely it could have been better. The first was the best in my opinion. But since we're talking about Storm 4, it has a way better fighting system than One Piece BB. Online is better. Story mode is much more immersive than Burning Blood's simply because of the boss battles. They're amazing in Storm 4, they really up'ed it with those battles. And it has a adventure mode along with the story mode where you can roam around the Leaf Village and complete quests. If you buy the Boruto DLC, you can have a lot of more side quests to play as well. And simply to put the cherry on top, Naruto Storm 4 looks so much better (graphically-wise) than BB.
So I'd easily go with Naruto Storm 4 if you're choosing between the games. Only get BB if on sale. 20 bucks at max, tbh.
(This is only my opinion btw..)
(Oh and if you are on Steam, Naruto Storm 4 is on sale for 15 bucks as well, if that helps)
Happy gaming.
