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
Comic-panel beat 'em up notorious for punishing health drain and tough fights.

Execution · Pure Mechanics
Tests execution against dense scripted boss patterns in handheld run-and-gun form.
Comix Zone leans Execution (Pure Mechanics); Gunstar Super Heroes 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.
Comix Zone
Brutal one-life brawling demands clean play
Gunstar Super Heroes
Dense run-and-gun action demands precise dodging and weapon control
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Comix Zone
Enemies follow fixed attack scripts
Gunstar Super Heroes
Boss patterns are elaborate but completely scripted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Comix Zone
Everything is placed and scripted
Gunstar Super Heroes
Stages play out identically each run
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Comix Zone
Panel routes and item use are memorizable
Gunstar Super Heroes
Learning screen-filling boss movesets is the core progression
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.