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

Optimization · Systems & Chaos
Racing the day cycle to stack items faster than the seed punishes you.

Optimization · Practiced Mastery
Routing efficient digs and upgrades through a randomised mine.
Muck leans Optimization (Systems & Chaos); SteamWorld Dig leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Muck
Kiting bosses and dodging demands basic action skill
SteamWorld Dig
Digging and platforming need modest precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Muck
Enemies swarm on simple scripts
SteamWorld Dig
Enemies follow simple fixed patterns
Muck leans a little harder on variance, though the gap is small.
Muck
Seeds, chest rolls and item drops shape every run
SteamWorld Dig
Randomised mine layouts hide ore and hazards each run
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Muck
Power-stacking economy and day-loop routing decide survival
SteamWorld Dig
Upgrade routing and efficient dig paths drive progress
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.