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 · Competitive PvP
A class-based objective shooter remembered for its parkour movement and rocky launch.

Execution · Competitive PvP
Blockbuster 2009 sequel famous for killstreak chains and frantic multiplayer.
Brink leans Execution (Competitive PvP); Call of Duty: Modern Warfare 2 leans Execution (Competitive PvP).
Call of Duty: Modern Warfare 2 leans a little harder on execution, though the gap is small.
Brink
SMART parkour and gunfights demand FPS mechanics
Call of Duty: Modern Warfare 2
Fast time-to-kill rewards raw aim and reflex
Call of Duty: Modern Warfare 2 leans a little harder on reads, though the gap is small.
Brink
Human teams contest objectives and flank routes
Call of Duty: Modern Warfare 2
Outguessing human rotations and flanks
Call of Duty: Modern Warfare 2 leans a little harder on variance, though the gap is small.
Brink
Spawn and objective chaos adds noise
Call of Duty: Modern Warfare 2
Spawn flips and killstreak randomness
Call of Duty: Modern Warfare 2 leans a little harder on optimization, though the gap is small.
Brink
Class loadouts and objective timing are learnable
Call of Duty: Modern Warfare 2
Killstreak economy, loadout and map knowledge
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.