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 · Practiced Mastery
The original 2003 WWII shooter built around cinematic squad set pieces.

Execution · Practiced Mastery
Browser tank duels mixing aim, human positioning reads, and upgrade grind.
Call of Duty leans Execution (Practiced Mastery); Tanki Online leans Execution (Practiced Mastery).
Call of Duty leans a little harder on execution, though the gap is small.
Call of Duty
Aim and reaction carry the scripted firefights
Tanki Online
Aiming turrets and dodging shells decides duels
Tanki Online leans a little harder on reads, though the gap is small.
Call of Duty
Light multiplayer prediction; campaign AI is scripted
Tanki Online
Human tankers feint around corners and flag routes
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty
Some spawn and hit unpredictability
Tanki Online
Spawns and drops add light battlefield noise
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty
Memorising set pieces and weapon positions
Tanki Online
Equipment upgrades and loadout economy gate the grind
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.