head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Second Sight demands more optimization.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Optimization · Practiced Mastery
Planning stealth routes and psychic-power use through scripted guard patrols.
Grand Theft Auto V leans Execution (Practiced Mastery); Second Sight 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.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Second Sight
Aiming and psychic-power juggling under fire need moderate hands
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Second Sight
Guard AI runs predictable patrol scripts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Some mission and lobby randomness.
Second Sight
Patrol routes are unknown only on first pass
Second Sight leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Second Sight
Planning stealth routes and power usage solves each level
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.