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
Treasure's Mega Drive boss-rush gauntlet demanding flawless execution against giant setpieces.

Execution · Pure Mechanics
Memorising brutal scripted patterns and executing them without a single slip.
Alien Soldier leans Execution (Pure Mechanics); Contra: Hard Corps 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.
Alien Soldier
Frame-tight dodges across thirty-plus bosses
Contra: Hard Corps
One-hit deaths under relentless bullet pressure demand perfect inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Alien Soldier
Bosses fully scripted
Contra: Hard Corps
Bosses are fully scripted setpieces
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Alien Soldier
Nothing hidden after one loop
Contra: Hard Corps
Everything fixed once routes and patterns are known
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Alien Soldier
Weapon loadout and moveset mastery solvable
Contra: Hard Corps
Memorising boss patterns, weapons and branching routes is mandatory
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.