head to head
Neither is simply harder - they are hard in different places. Garry's Mod demands more execution; Use Your Words demands more reads.

Reads · Light / Casual
Source-engine sandbox whose community modes range from building to social deduction.

Reads · Bluff & Deduction
A party game where players write funny answers and vote on the best.
Garry's Mod leans Reads (Light / Casual); Use Your Words leans Reads (Bluff & Deduction).
Garry's Mod leans clearly harder on execution.
Garry's Mod
Varies by mode; base sandbox is undemanding
Use Your Words
Typing jokes; no dexterity test.
Use Your Words leans clearly harder on reads.
Garry's Mod
Social deduction modes like TTT involve humans
Use Your Words
Tailoring humor and decoys to the room wins votes.
Use Your Words leans a little harder on variance, though the gap is small.
Garry's Mod
Hidden roles and player chaos in popular modes
Use Your Words
Random prompts and voter mood swing results.
Garry's Mod leans a little harder on optimization, though the gap is small.
Garry's Mod
Contraption building rewards systems knowledge
Use Your Words
Minimal solvable structure; comedy heuristics only.
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.