Slot is clearly a more addictive game. It's runs 24/7 compared to sports games where there are breaks. If a gambler don't take a break then the fixtures of the games if give the gambler break since sports games are not played everyday.
That's a big reason why slots is more addictive, there's no other way, it's just that players and gamblers focus more on one activity because of taste, some like slots more and others like sports betting, I think that's where the difference can be made, but I think both activities when practiced without control cause addiction.