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
Zero awakens to lead a resistance in a harsh, rank-graded GBA action series debut.

Execution · Practiced Mastery
Combo execution layered over solving each park's optimal scoring line.
Mega Man Zero leans Execution (Practiced Mastery); Tony Hawk's Underground 2 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.
Mega Man Zero
Punishing GBA action with strict ranking on damage
Tony Hawk's Underground 2
Combo timing, balance meters and manuals demand practiced hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Mega Man Zero
All bosses are pattern-based
Tony Hawk's Underground 2
No opponent adapts; score attack is solo
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mega Man Zero
Cyber-elf locations hidden at first
Tony Hawk's Underground 2
Maps and goals are fixed and fully knowable
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Mega Man Zero
Rank system penalises elf use, rewarding optimised clean runs
Tony Hawk's Underground 2
Finding the highest-scoring line through each park is 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.