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.

Optimization · Practiced Mastery
Series finale blending stealth with active battlefields and heavy cinematics.

Execution · Practiced Mastery
Looking Glass's 1996 squad-command sim of powered-armor combat on alien battlefields.
Metal Gear Solid 4: Guns of the Patriots leans Optimization (Practiced Mastery); Terra Nova: Strike Force Centauri leans Execution (Practiced Mastery).
Terra Nova: Strike Force Centauri leans a little harder on execution, though the gap is small.
Metal Gear Solid 4: Guns of the Patriots
flexible gunplay alongside sneaking
Terra Nova: Strike Force Centauri
Piloting powered armor and aiming under fire is demanding
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Gear Solid 4: Guns of the Patriots
battlefield factions act on scripts
Terra Nova: Strike Force Centauri
Enemy forces follow mission scripts, never adapt
Terra Nova: Strike Force Centauri leans a little harder on variance, though the gap is small.
Metal Gear Solid 4: Guns of the Patriots
mid-battle chaos mostly cosmetic
Terra Nova: Strike Force Centauri
Unknown enemy placements on first mission attempts
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Gear Solid 4: Guns of the Patriots
camo, gear, and route knowledge per act
Terra Nova: Strike Force Centauri
Squad orders, loadouts and approach routes are plannable
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.
full breakdown
Metal Gear Solid 4: Guns of the Patriots →
full breakdown
Terra Nova: Strike Force Centauri →