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

Optimization · Practiced Mastery
Chaotic co-op kitchen game solved by ruthless division of labor.

Execution · Practiced Mastery
Looking Glass's 1996 squad-command sim of powered-armor combat on alien battlefields.
Overcooked leans Optimization (Practiced Mastery); Terra Nova: Strike Force Centauri leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Overcooked
Chopping, carrying, and plating under the clock
Terra Nova: Strike Force Centauri
Piloting powered armor and aiming under fire is demanding
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Overcooked
Kitchens don't adapt; teammates aren't opponents
Terra Nova: Strike Force Centauri
Enemy forces follow mission scripts, never adapt
Terra Nova: Strike Force Centauri leans a little harder on variance, though the gap is small.
Overcooked
Order queue randomness within known sets
Terra Nova: Strike Force Centauri
Unknown enemy placements on first mission attempts
Overcooked leans a little harder on optimization, though the gap is small.
Overcooked
Station assignment and task routing win stars
Terra Nova: Strike Force Centauri
Squad orders, loadouts and approach routes are plannable
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.