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.

Optimization · Practiced Mastery
Slingshot trajectory puzzles with randomised bird hands gating consistency.

Optimization · Practiced Mastery
Routing efficient digs and upgrades through a randomised mine.
Angry Birds 2 leans Optimization (Practiced Mastery); 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.
Angry Birds 2
Trajectory precision on the slingshot matters modestly
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.
Angry Birds 2
Pigs sit in structures, never adapting
SteamWorld Dig
Enemies follow simple fixed patterns
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Angry Birds 2
Random bird-card hands and multi-stage levels shuffle each attempt
SteamWorld Dig
Randomised mine layouts hide ore and hazards each run
SteamWorld Dig leans a little harder on optimization, though the gap is small.
Angry Birds 2
Knowing structure weak points and bird matchups is the edge
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.