head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Practiced Mastery
Crisp NES licensed platformer about chipmunks hurling crates at robots.

Execution · Practiced Mastery
The most demanding of the New Super Mario line, with brutal optional challenges.
Chip 'n Dale Rescue Rangers leans Execution (Practiced Mastery); New Super Mario Bros. U leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Chip 'n Dale Rescue Rangers
Tight jumps and box-throw timing
New Super Mario Bros. U
Challenge modes demand tight, precise platforming
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Chip 'n Dale Rescue Rangers
Enemies are simple fixed patterns
New Super Mario Bros. U
All enemy behavior is scripted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Chip 'n Dale Rescue Rangers
Deterministic levels
New Super Mario Bros. U
Deterministic level layouts
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Chip 'n Dale Rescue Rangers
Level memory and boss pattern knowledge
New Super Mario Bros. U
Routing star coins and secret world shortcuts
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.