head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Competitive PvP
Mechanical football control plus predicting how a human opponent attacks.

Execution · Competitive PvP
Tests shot timing and faking out human defenders amid item-driven chaos.
FIFA 16 leans Execution (Competitive PvP); Mario Strikers Charged leans Execution (Competitive PvP).
FIFA 16 leans a little harder on execution, though the gap is small.
FIFA 16
Dribbling, defending and finishing inputs decide duels
Mario Strikers Charged
Timing tackles, charged shots and goalie deflections needs quick hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA 16
Human opponents online adapt tactics match to match
Mario Strikers Charged
Versus humans, faking shots and baiting tackles drives goals
Mario Strikers Charged leans a little harder on variance, though the gap is small.
FIFA 16
Deflections and finishing randomness swing close games
Mario Strikers Charged
Items and stage hazards inject swingy chaos into matches
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA 16
Formations and squad construction reward study
Mario Strikers Charged
Captain abilities and team builds reward knowing the systems
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.