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.
Yeah, we can't actually come to a definite conclusion that it's slot of sports betting that gamblers get addicted from the most, because addiction comes from our actions, how we treat something.
It is true that football is seasonal but then, there is always a club or team of league playing football at any given point in time, if at all worst come to worst, there is no football game available to bet on, an addicted gambler in a bid to satisfy his or her cravings can bet on any other available sports game like basketball, table tennis, hockey and so on.
So whether slot of football games/sports betting, addiction is addiction and any body can get addicted playing any of this two types of gambling game, it all depends on their approach.