head to head
Guns Up! asks more than Portal, and the gap is reads.

Optimization · Pure Optimization
A side-scrolling strategy game about optimizing base defense and attacking opponents.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Guns Up! leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans a little harder on execution, though the gap is small.
Guns Up!
Light real-time card placement, not twitch-driven
Portal
Portal placement timing modest.
Guns Up! leans clearly harder on reads.
Guns Up!
Attacking human bases means anticipating their defense layouts
Portal
No adversary modeling player.
Guns Up! leans clearly harder on variance.
Guns Up!
Card draws and unit timing add randomness
Portal
Deterministic chambers; no randomness.
Portal leans a little harder on optimization, though the gap is small.
Guns Up!
Base layout and army composition is the core test
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.