Building comparison
head to head
Garry's ModvsTabletop Simulator
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.
Garry's Mod
Reads · Light / Casual
Source-engine sandbox whose community modes range from building to social deduction.
Tabletop Simulator
Reads · Bluff & Deduction
A physics sandbox whose actual skill test is whatever board game you load into it.
Garry's Mod leans Reads (Light / Casual); Tabletop Simulator leans Reads (Bluff & Deduction).
Garry's ModTabletop Simulator
Axis by axis
Execution2 vs 1
Garry's Mod leans a little harder on execution, though the gap is small.
Garry's Mod
Varies by mode; base sandbox is undemanding
Tabletop Simulator
Fiddly physics manipulation, never a skill ceiling
Reads3 vs 4
Tabletop Simulator leans a little harder on reads, though the gap is small.
Garry's Mod
Social deduction modes like TTT involve humans
Tabletop Simulator
Depends entirely on the tabletop game played with humans
Variance3 vs 4
Tabletop Simulator leans a little harder on variance, though the gap is small.
Garry's Mod
Hidden roles and player chaos in popular modes
Tabletop Simulator
Dice and shuffled decks supply whatever randomness the game has
Optimization3 vs 3
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Garry's Mod
Contraption building rewards systems knowledge
Tabletop Simulator
Strategy lives in the hosted game, not the simulator
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.