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.

Execution · Practiced Mastery
A fast mech-action game where assembling the right build and piloting it hard both decide bosses.

Execution · Practiced Mastery
An arcade FPS that scores you for killing enemies in the most creative ways possible.
Armored Core VI: Fires of Rubicon leans Execution (Practiced Mastery); Bulletstorm 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.
Armored Core VI: Fires of Rubicon
Boss fights demand sharp dodges and stagger timing
Bulletstorm
Leash, kick, and shot timing drive skillshot chains
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Armored Core VI: Fires of Rubicon
Campaign bosses are scripted; PvP is niche
Bulletstorm
Enemies are scripted fodder for your combos
Bulletstorm leans a little harder on variance, though the gap is small.
Armored Core VI: Fires of Rubicon
Fixed encounters
Bulletstorm
Arenas and spawns are fixed and learnable
Armored Core VI: Fires of Rubicon leans a little harder on optimization, though the gap is small.
Armored Core VI: Fires of Rubicon
Build crafting trivializes many bosses
Bulletstorm
Maximising skillshot score per arena is a solvable puzzle
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.