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 · Pure Mechanics
A bullet-hell shooter testing precision dodging through dense scripted patterns.

Execution · Pure Mechanics
A loud, high-endurance test of accurate crowd control against relentless scripted enemy swarms in open arenas.
Bullet Heaven 2 leans Execution (Pure Mechanics); Serious Sam: The First Encounter leans Execution (Pure Mechanics).
Bullet Heaven 2 leans a little harder on execution, though the gap is small.
Bullet Heaven 2
Dodging dense bullet patterns is the whole game
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.
Bullet Heaven 2
Bosses fire scripted patterns, not adaptive
Serious Sam: The First Encounter
All enemies are scripted and follow fixed rush patterns
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Bullet Heaven 2
Item drops add minor randomness
Serious Sam: The First Encounter
Enemy placement is consistent across runs; no hidden information
Bullet Heaven 2 leans a little harder on optimization, though the gap is small.
Bullet Heaven 2
Character and weapon choice optimize survival underneath
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.