It’s almost impossible with sports betting, but very possible with slots.
Isn't it the other way around? It's easy to win on sports betting, albeit even in parlay, it might not be as huge but maybe a 5x-10x parlay could be hit by anyone here. As compare to slot machine players hitting a 1000x. Although there could be accomplished as we have seen multiplier competitions hitting that huge number, but still everything is base on luck.
So for me, it's parlay bets over slot machine multiplier. I love slot games, don't get me wrong, but the chances and again it will take lady luck to be in your side to hit a huge multiplier in slot games and it's really hard to duplicate that kind of feat.
I also think that if I was looking for huge multipliers, I would prefer the parlay instead of the slots. Even if you can hit great multipliers in slots, you usually only stake a few cents per spin to have more tries, which makes the prize smaller. With big parlays, on the contrary, your chances of winning are near zero, but a bet of one or two bucks can change your life if you are extremely lucky.