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
The side-scrolling shmup now immortal for its 'all your base' intro.
Comix Zone leans Execution (Pure Mechanics); Zero Wing 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
Zero Wing
Bullet weaving and tractor-beam captures under fire
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
Zero Wing
Enemy waves fully 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
Zero Wing
Deterministic patterns every 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
Zero Wing
Memorising wave layouts and power-up routes
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.