I think its football. There are just so many aspects to a team. You got to find the right QB, RB, OL, WR, ad TE. Then you got to the defense. Oh but dont forget special teams! How many times hav we seen teams lose big games due to an inefficient kicker?
Its just so many different individualized positions in football. Basketball, everybody plays offense and defense, and you really only worried bout 9 dudes really. And injuries are such a huge factor in football.
The one big advantage football has over basketball whe it comes to building team is non-guaranteed contracts. In football, if a player gets hurt or turns to

status, you can just cut him. In basketball, you're stuck.