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 · Practiced Mastery
Moody Halo side story about ordinary troopers piecing together a night in New Mombasa.

Execution · Practiced Mastery
An over-the-top horde shooter throwing hundreds of charging enemies at you.
Halo 3: ODST leans Execution (Practiced Mastery); Serious Sam: The Second Encounter leans Execution (Practiced Mastery).
Serious Sam: The Second Encounter leans a little harder on execution, though the gap is small.
Halo 3: ODST
Squishier soldier demands careful aim and positioning
Serious Sam: The Second Encounter
Circle-strafing huge horde waves tests stamina and aim
Halo 3: ODST leans a little harder on reads, though the gap is small.
Halo 3: ODST
Covenant patrols are scripted, not adaptive
Serious Sam: The Second Encounter
Enemies charge in fixed patterns
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Halo 3: ODST
Open Mombasa hides clues until found
Serious Sam: The Second Encounter
Wave compositions memorised after one run
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Halo 3: ODST
Firefight wave knowledge and route planning
Serious Sam: The Second Encounter
Prioritising targets and managing arenas is solvable
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.