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

Execution · Pure Mechanics
Arcade run-and-gun reflexes against fully memorisable boss patterns.

Execution · Pure Mechanics
Final Fantasy music rhythm game layering light RPG party building over note charts.
Sunset Riders leans Execution (Pure Mechanics); Theatrhythm Final Bar Line leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Sunset Riders
Dodging bullet spreads and snap-shooting bosses is everything
Theatrhythm Final Bar Line
Note timing accuracy on Ultimate charts
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Sunset Riders
Bandits and bosses cycle memorisable arcade patterns
Theatrhythm Final Bar Line
Fixed charts, no opponent
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Sunset Riders
Spawns are deterministic each credit
Theatrhythm Final Bar Line
Quest drops are random, gameplay is deterministic
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Sunset Riders
Pattern memorisation for one-credit clears is the meta-game
Theatrhythm Final Bar Line
Party builds and abilities optimize quest clears
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.