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
Dodging scripted bullet waves while grinding an upgrade economy to brute-force medals.
Comix Zone leans Execution (Pure Mechanics); Sky Force Anniversary 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
Sky Force Anniversary
Weaving dense bullet patterns is the entire moment-to-moment test
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
Sky Force Anniversary
Enemy waves follow fixed scripts every run
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
Sky Force Anniversary
Spawns are deterministic; almost nothing to map
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
Sky Force Anniversary
Upgrade grinding and medal-route planning shape 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.