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
Futuristic large-scale Battlefield where teams besiege flying Titan carriers.

Execution · Competitive PvP
Blockbuster 2009 sequel famous for killstreak chains and frantic multiplayer.
Battlefield 2142 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.
Battlefield 2142
Gunplay, piloting, and Titan boarding need solid 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.
Battlefield 2142
64-player human teams shift fronts and Titan assaults
Call of Duty: Modern Warfare 2
Outguessing human rotations and flanks
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 2142
Large maps hide flanks; battle chaos obscures information
Call of Duty: Modern Warfare 2
Spawn flips and killstreak randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 2142
Unlock paths, squad roles, and Titan strategy reward planning
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.