head to head
Call of Duty: Modern Warfare 2 asks more than Agar.io, and the gap is execution.

Reads · Competitive PvP
A browser arena where your cell eats smaller players and flees bigger ones.

Execution · Competitive PvP
Blockbuster 2009 sequel famous for killstreak chains and frantic multiplayer.
Agar.io leans Reads (Competitive PvP); Call of Duty: Modern Warfare 2 leans Execution (Competitive PvP).
Call of Duty: Modern Warfare 2 leans clearly harder on execution.
Agar.io
Mouse steering and split timing
Call of Duty: Modern Warfare 2
Fast time-to-kill rewards raw aim and reflex
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Agar.io
Baiting and predicting human blobs decides fights
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.
Agar.io
Spawn locations and lobby makeup random
Call of Duty: Modern Warfare 2
Spawn flips and killstreak randomness
Call of Duty: Modern Warfare 2 leans clearly harder on optimization.
Agar.io
Split-merge math is shallow but real
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.