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.
I think sports betting also base on luck because if you are not lucky you never make any good profit in sports betting.. and odds in sports betting is difference than a gambling casino base in luck and most of them are 1% odds like in dice games..
So more risky in gambling casino and in sports betting risky but not too risky the same as casino gambling..
When it comes to risk then casino gambling does have higher compared on sports betting because betting on sports somehow need analysis and experience to increase your winning chance on a certain game which is different on playing casino which those games are normally dependent on luck only which we can really see the difference on both sides.