head to head
Call of Duty: Modern Warfare 2 asks more than PlayStation All-Stars Battle Royale, and the gap is execution.

Execution · Competitive PvP
Blockbuster 2009 sequel famous for killstreak chains and frantic multiplayer.

Execution · Competitive PvP
Sony's mascot brawler where only Super attacks score kills, making meter management the whole game.
Call of Duty: Modern Warfare 2 leans Execution (Competitive PvP); PlayStation All-Stars Battle Royale leans Execution (Competitive PvP).
Call of Duty: Modern Warfare 2 leans clearly harder on execution.
Call of Duty: Modern Warfare 2
Fast time-to-kill rewards raw aim and reflex
PlayStation All-Stars Battle Royale
Combo routes into Super meter need decent but modest hands.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare 2
Outguessing human rotations and flanks
PlayStation All-Stars Battle Royale
Super-only kills make baiting human opponents the core decision.
Call of Duty: Modern Warfare 2 leans a little harder on variance, though the gap is small.
Call of Duty: Modern Warfare 2
Spawn flips and killstreak randomness
PlayStation All-Stars Battle Royale
Items and four-player chaos add mild randomness.
Call of Duty: Modern Warfare 2 leans a little harder on optimization, though the gap is small.
Call of Duty: Modern Warfare 2
Killstreak economy, loadout and map knowledge
PlayStation All-Stars Battle Royale
Meter-build efficiency per character is the solvable layer.
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.