head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Practiced Mastery
Precision sniping and arena navigation through fixed, gimmick-laden levels.

Execution · Pure Mechanics
A simple arcade rail shooter testing aim and reaction against scripted waves.
MDK leans Execution (Practiced Mastery); Sky Destroyer leans Execution (Pure Mechanics).
Sky Destroyer leans a little harder on execution, though the gap is small.
MDK
Sniper-mode precision and arena dodging demand steady hands
Sky Destroyer
Aiming and dodging on rails is the entire test
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
MDK
Alien enemies behave on fixed scripts
Sky Destroyer
Enemy planes fly scripted attack runs
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
MDK
Levels are authored with nothing random
Sky Destroyer
Stages repeat predictably once seen
MDK leans a little harder on optimization, though the gap is small.
MDK
Learning arena gimmicks and item use solves each level
Sky Destroyer
Little to plan beyond learning spawn patterns
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.