head to head
Neither is simply harder - they are hard in different places. Red Dead Redemption 2 demands more variance; Tony Hawk's Underground demands more execution.

Execution · Practiced Mastery
A cinematic open-world western leaning on shooting feel and atmosphere.

Execution · Practiced Mastery
A story-driven skateboarding game still won by trick execution.
Red Dead Redemption 2 leans Execution (Practiced Mastery); Tony Hawk's Underground leans Execution (Practiced Mastery).
Tony Hawk's Underground leans clearly harder on execution.
Red Dead Redemption 2
Gunplay and Dead Eye reward aim and timing.
Tony Hawk's Underground
Combos plus off-board tricks keep the input ceiling high
Red Dead Redemption 2 leans a little harder on reads, though the gap is small.
Red Dead Redemption 2
Enemies use scripted AI patterns, not adaptation.
Tony Hawk's Underground
Story missions are scripted, not adaptive
Red Dead Redemption 2 leans clearly harder on variance.
Red Dead Redemption 2
Some hunting and weather randomness, lightly hidden.
Tony Hawk's Underground
Fixed levels and mission scripts
Tony Hawk's Underground leans clearly harder on optimization.
Red Dead Redemption 2
Loadouts and routes solvable but loose.
Tony Hawk's Underground
Mission and score-line routing remain 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.