head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Shin Megami Tensei: Devil Survivor 2 - Record Breaker demands more variance.

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

Optimization · Pure Optimization
Tests demon-fusion team building and tactical grid optimization against scripted encounter design.
Portal leans Optimization (Pure Optimization); Shin Megami Tensei: Devil Survivor 2 - Record Breaker leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Shin Megami Tensei: Devil Survivor 2 - Record Breaker
Turn-based menus - hands are irrelevant
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.
Shin Megami Tensei: Devil Survivor 2 - Record Breaker
Enemy AI follows mappable priorities, never models you
Shin Megami Tensei: Devil Survivor 2 - Record Breaker leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Shin Megami Tensei: Devil Survivor 2 - Record Breaker
Demon auction and skill cracks add manageable RNG
Shin Megami Tensei: Devil Survivor 2 - Record Breaker leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Shin Megami Tensei: Devil Survivor 2 - Record Breaker
Team building, fusion and grid positioning are deeply 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.