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

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

Execution · Pure Mechanics
Wrestling motion-control aim and swordplay through fixed scripted shootouts.
MDK leans Execution (Practiced Mastery); Red Steel 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.
MDK
Sniper-mode precision and arena dodging demand steady hands
Red Steel
Wiimote aiming and sword swings are the whole physical 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
Red Steel
Enemies are scripted spawns, never adaptive
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
Red Steel
Encounters are fixed once seen
MDK leans a little harder on optimization, though the gap is small.
MDK
Learning arena gimmicks and item use solves each level
Red Steel
Light level memorisation and weapon choices
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.