head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Viva Piñata: Trouble in Paradise demands more variance.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.

Optimization · Pure Optimization
The expanded sequel adds desert and arctic piñatas to the garden-ecosystem puzzle.
Portal leans Optimization (Pure Optimization); Viva Piñata: Trouble in Paradise leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Viva Piñata: Trouble in Paradise
Same gentle gardening controls
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
No adversary modeling player.
Viva Piñata: Trouble in Paradise
Creature behavior is rule-based, not adaptive
Viva Piñata: Trouble in Paradise leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Viva Piñata: Trouble in Paradise
New biome visitors still arrive with some chance
Portal leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Viva Piñata: Trouble in Paradise
Expanded species web deepens the requirement-solving game
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.