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

Execution · Practiced Mastery
Aim and movement through a fully scripted campaign that route knowledge solves.

Execution · Practiced Mastery
Tests isometric jump precision and room-by-room spatial puzzle reading.
Half-Life: Source leans Execution (Practiced Mastery); Lumo 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.
Half-Life: Source
Aim, movement and platforming through Black Mesa's gauntlets
Lumo
Isometric jumps with tricky perspective punish imprecision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life: Source
Marines and aliens run impressive but fixed scripts
Lumo
Rooms are fixed challenges with no opponent
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life: Source
Fully authored campaign, nothing random
Lumo
Secrets hide only until the room is studied
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life: Source
Route knowledge and resource management trivialise replays
Lumo
Each chamber is a solvable spatial puzzle
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.