head to head
Neither is simply harder - they are hard in different places. Battle Chasers: Nightwar demands more variance; Portal demands more execution.

Optimization · Pure Optimization
Optimising party builds and turn economy through dungeons with light layout randomness.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Battle Chasers: Nightwar leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Battle Chasers: Nightwar
Turn-based commands have no twitch demands
Portal
Portal placement timing modest.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Battle Chasers: Nightwar
Dungeon enemies follow fixed scripts, nothing adapts
Portal
No adversary modeling player.
Battle Chasers: Nightwar leans clearly harder on variance.
Battle Chasers: Nightwar
Randomly arranged dungeon rooms and loot shuffle each run
Portal
Deterministic chambers; no randomness.
Portal leans a little harder on optimization, though the gap is small.
Battle Chasers: Nightwar
Overcharge management, party builds and turn order are solvable math
Portal
Pure puzzle-solving optimization.
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.