This questions and comparison between pvp and casino games might not be fair, and this is because -
Pvp games requires a good level of skill to be able to win, while casino games on the other hand is purely luck based, those who lack the skill to challenge or play against other gamblers will definitely settle for casino games, while those who have the skill winning the game requires will choose to settle with pvp games..

But if I was asked to make a choice as to which I think is more fun to play, I would prefer pvp games over casino games, I think nothing is more fun in gambling than challenging other players.