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 · Twitch Chaos
Rapid-fire reflex bursts against randomised waves in ten-second chunks.

Execution · Pure Mechanics
Rapid-fire recognition and reaction across hundreds of five-second microgames.
Shutshimi leans Execution (Twitch Chaos); WarioWare, Inc.: Mega Microgame$! leans Execution (Pure Mechanics).
WarioWare, Inc.: Mega Microgame$! leans a little harder on execution, though the gap is small.
Shutshimi
Ten-second waves demand instant dodging and target triage
WarioWare, Inc.: Mega Microgame$!
Reacting correctly in five-second microgames is the entire challenge
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Shutshimi
Enemies spawn from random tables, not a mind
WarioWare, Inc.: Mega Microgame$!
No adaptive opponent - microgames are scripted
Shutshimi leans a little harder on variance, though the gap is small.
Shutshimi
Randomised waves and absurd power-ups reshape every run
WarioWare, Inc.: Mega Microgame$!
Random microgame order forces instant recognition each round
Shutshimi leans a little harder on optimization, though the gap is small.
Shutshimi
Upgrade choices under time pressure are a thin layer
WarioWare, Inc.: Mega Microgame$!
Each microgame's solution is trivial once seen
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.