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

Execution · Practiced Mastery
Remake of the original Metroid with modern movement and a stealth epilogue.

Execution · Practiced Mastery
Memorising stage routes and executing them cleanly for ranks and speed.
Metroid: Zero Mission leans Execution (Practiced Mastery); Sonic Adventure 2: Battle 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.
Metroid: Zero Mission
polished 2D movement plus a stealth finale
Sonic Adventure 2: Battle
Speed-stage control and rail precision reward clean hands
Sonic Adventure 2: Battle leans a little harder on reads, though the gap is small.
Metroid: Zero Mission
enemies and pirates are scripted
Sonic Adventure 2: Battle
Two-player battles exist but stay shallow and scripted
Metroid: Zero Mission leans a little harder on variance, though the gap is small.
Metroid: Zero Mission
hidden passages unknown only once
Sonic Adventure 2: Battle
Stages are fixed; Chao stats are deterministic grinding
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid: Zero Mission
sequence breaks and route optimization are celebrated
Sonic Adventure 2: Battle
Rank chasing means memorising routes and score lines
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.