head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Pure Mechanics
Dodging scripted bullet patterns with stage memorisation doing the planning.

Execution · Pure Mechanics
Comic-panel beat 'em up notorious for punishing health drain and tough fights.
Air Buster leans Execution (Pure Mechanics); Comix Zone leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Air Buster
Bullet weaving and tight corridors demand precise control
Comix Zone
Brutal one-life brawling demands clean play
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Air Buster
Enemy waves are fully scripted patterns
Comix Zone
Enemies follow fixed attack scripts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Air Buster
Spawns are deterministic once a credit is studied
Comix Zone
Everything is placed and scripted
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Air Buster
Memorising stage layouts and power-up routes drives clears
Comix Zone
Panel routes and item use are memorizable
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.