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
The most demanding of the New Super Mario line, with brutal optional challenges.

Execution · Practiced Mastery
Sonic alternates breakneck daytime boost stages with brawling night levels as the Werehog.
New Super Mario Bros. U leans Execution (Practiced Mastery); Sonic Unleashed 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.
New Super Mario Bros. U
Challenge modes demand tight, precise platforming
Sonic Unleashed
Daytime boost stages demand reaction-speed precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
New Super Mario Bros. U
All enemy behavior is scripted
Sonic Unleashed
Scripted enemies in both forms
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
New Super Mario Bros. U
Deterministic level layouts
Sonic Unleashed
First-run stage hazards arrive fast and unseen
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
New Super Mario Bros. U
Routing star coins and secret world shortcuts
Sonic Unleashed
S-rank routes and Werehog combat upgrades are solvable
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.