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

Optimization · Practiced Mastery
Backyard survival testing crafting optimisation with timing-based bug combat.

Optimization · Practiced Mastery
Methodically mapping a hostile station where knowledge and routing beat reflexes.
Grounded 2 leans Optimization (Practiced Mastery); System Shock leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Grounded 2
Dodging and perfect-blocking giant bugs takes real timing
System Shock
Combat and cyberspace ask competent but dated reflexes
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Grounded 2
Insect AI follows mappable behaviour patterns
System Shock
SHODAN's threats are scripted, not an adapting mind
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grounded 2
World discovery and resource spawns hide some information
System Shock
Citadel's layout and logs are hidden until uncovered
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Grounded 2
Base building, armor builds and tech routing drive progress
System Shock
Inventory, routing and station knowledge solve the 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.