If you are willing to study etc then they both are quite easy
Still i'd say sports betting is easier cause there it's only 3 chances with your bet: to win/lose or be voided while in usual fantasy football you must compete with other people and there only handful get prizes eventually ...
For example Fantasy Premier League is probably most well-known fantasy game in the world (besides North America) cause millions play that and so on.
There only very few people get prizes eventually but should you get it then it's absolutely worth it. Even some seasons ago someone from our country came 4th in overall standings there which clearly was very impressive result ...