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
Engineering self-sustaining closed-loop life support systems on a hostile planet against scripted environmental events.

Optimization · Pure Optimization
Juggling rival faction demands and island economics to keep your dictator in power.
Planetbase leans Optimization (Pure Optimization); Tropico 4 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.
Planetbase
Building placement is unhurried and menu-driven throughout
Tropico 4
Decree-clicking requires no dexterity
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Planetbase
No adversarial AI; threats are scripted event types
Tropico 4
Faction AI follows fixed ideological scripts, not player modeling
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Planetbase
Solar storm timing and resource availability add hidden pressure
Tropico 4
Random events and election outcomes inject meaningful uncertainty
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Planetbase
Power and oxygen loops are tightly engineered optimization puzzles
Tropico 4
Balancing factions, treasury, and production chains is the core loop
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.