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

Optimization · Pure Optimization
Hunting hidden objects and solving puzzles through a fixed mystery narrative.

Optimization · Pure Optimization
An open-ended needs-and-money system that rewards efficient scheduling.
Mystery Case Files: Fate's Carnival leans Optimization (Pure Optimization); The Sims leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Mystery Case Files: Fate's Carnival
Clicking objects has no twitch demand
The Sims
Clicking menus has no physical ceiling
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Mystery Case Files: Fate's Carnival
Solo with no opponent to model
The Sims
Sims run need-driven scripts, not minds
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mystery Case Files: Fate's Carnival
Hidden objects are fixed, just unfound until searched
The Sims
Event rolls add flavour, all quickly mapped
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Mystery Case Files: Fate's Carnival
Solving puzzles and finding items is the entire loop
The Sims
Need scheduling, career grinding and money loops are 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.