head to head
Neither is simply harder - they are hard in different places. Red Dead Redemption 2 demands more variance; TrackMania United Forever demands more execution.

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

Execution · Practiced Mastery
Pure time-trial racing testing relentless execution of an ever-more-optimised line.
Red Dead Redemption 2 leans Execution (Practiced Mastery); TrackMania United Forever leans Execution (Practiced Mastery).
TrackMania United Forever leans clearly harder on execution.
Red Dead Redemption 2
Gunplay and Dead Eye reward aim and timing.
TrackMania United Forever
Frame-perfect lines over hundreds of restarts are everything
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.
TrackMania United Forever
Time trials against ghosts - no one adapts to you
Red Dead Redemption 2 leans clearly harder on variance.
Red Dead Redemption 2
Some hunting and weather randomness, lightly hidden.
TrackMania United Forever
Deterministic physics with literally nothing hidden
TrackMania United Forever leans clearly harder on optimization.
Red Dead Redemption 2
Loadouts and routes solvable but loose.
TrackMania United Forever
Finding the theoretical fastest line is the meta-game
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.