I would say betting is growing more because you can find local betting shops literally everywhere, where people can go in and experience the vibe and excitement. There's always a league , such as the Premier League, Champions League, or World Cup, that people are engaged with, cheering for their clubs and countries. So they are mostly betting on sports games.
On the other hand, casinos are not as available while there are some places with nice casinos to chill in, they're not always readily available. Where I stay now, casinos are not handy; betting shops are more and so people seem more attached to betting than casinos, unless they want to play online. Aside from the youth, elderly people might not have the time or flexibility to play casino games on their phones. Overall, I think betting is growing wider.
I also join those who think that bets are more widely distributed than casinos. I have not conducted a study, but I think that for every thousand fans and spectators of the Champions League, a very large percentage of those who place bets, testing their rightness with money. And a casino is just an institution that you can go to from time to time, and sometimes even forget about its existence if there is no need for it or you run out of money. Football fans have many Leagues that are almost never interrupted, and on sports channels the game is constantly and every day. Sports betting still has a different nature than casinos and I think that in the end the bets will win the battle, because they are associated with the favorite teams of the players, and not just testing their luck, it is something more.