Casino is way more risky for sure. In casino it's all about luck and sometimes RNG, while in sport bets you can predict better who might win now, because you can find statistics about team and players in that team, while best statistic you can find in casino is "lucky" numbers list, which is not helping you at all. Basketball game with 95% chance to win will probably win, while in casino you can't be 100% if you will win
you can bet 95% odds in casino as well. just bet everything on a roulette wheel except 1 or 2 numbers.
But chances that it will roll on that 1 number that you don't bet on is much higher than team that have 95% chance to win. Teams like this are usually stronger, faster and plays better than enemy team, and they will almost always win, while when you bet on roulette, ball have same chance to stop on each number so it makes gambling like this much riskier