head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is optimization, and it is a single point.

Execution · Practiced Mastery
The fastest mainline Souls, distilling the formula into aggressive boss duels.

Execution · Practiced Mastery
A one-hit boss-rush where solving each titan still demands perfect execution.
Dark Souls III leans Execution (Practiced Mastery); Titan Souls 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.
Dark Souls III
fast roll timing against aggressive scripted bosses
Titan Souls
One arrow, one hit point; every shot must be perfect
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dark Souls III
PvP invasions exist but are optional
Titan Souls
Bosses are scripted patterns, not adaptive minds
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dark Souls III
fixed encounters converge after first sight
Titan Souls
Unknown boss gimmicks only on first attempts
Dark Souls III leans a little harder on optimization, though the gap is small.
Dark Souls III
movesets and builds are fully mappable
Titan Souls
Each titan has a solvable weak-point strategy
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.