head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Optimization · Pure Optimization
The Game Boy expedition that turns Metroid into a methodical extermination checklist deep inside SR388.

Optimization · Pure Optimization
Planning stealth routes around fully mappable guard patterns.
Metroid II: Return of Samus leans Optimization (Pure Optimization); Thief leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid II: Return of Samus
Cramped Game Boy combat against Metroid forms.
Thief
Movement timing matters but shadows forgive imprecision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid II: Return of Samus
Creatures follow fixed behaviours.
Thief
Guards patrol fixed routes with mappable vision cones
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid II: Return of Samus
Disorienting unknown caverns until mapped.
Thief
Patrol layouts are scripted-but-unknown on first entry
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid II: Return of Samus
Hunting all 39 Metroids is methodical route work.
Thief
Route planning around guard patterns is the whole game
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.