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 · Pure Mechanics
A test of fast, precise shooting and map navigation against scripted but relentless enemies.

Execution · Pure Mechanics
A loud, high-endurance test of accurate crowd control against relentless scripted enemy swarms in open arenas.
Doom (1993) leans Execution (Pure Mechanics); Serious Sam: The First Encounter leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Doom (1993)
Precise movement and shooting against relentless enemy pressure
Serious Sam: The First Encounter
Sustained accurate fire against enormous enemy hordes demands constant aim
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Doom (1993)
Enemies follow scripted patrol and attack patterns, not adaptive
Serious Sam: The First Encounter
All enemies are scripted and follow fixed rush patterns
Doom (1993) leans a little harder on variance, though the gap is small.
Doom (1993)
Enemy placement is fixed but unknown on first run through levels
Serious Sam: The First Encounter
Enemy placement is consistent across runs; no hidden information
Doom (1993) leans a little harder on optimization, though the gap is small.
Doom (1993)
Level routing and resource management determine survival efficiency
Serious Sam: The First Encounter
Enemy priority and positioning strategy are learnable but shallow
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.