head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Optimization · Pure Optimization
Alternate-history RTS where economy management and build orders win wars.

Optimization · Mind & Math
Norse-flavored RTS with tile control and seasonal pressure.
Command & Conquer: Red Alert leans Optimization (Pure Optimization); Northgard leans Optimization (Mind & Math).
Command & Conquer: Red Alert leans a little harder on execution, though the gap is small.
Command & Conquer: Red Alert
Micro and base management under time pressure
Northgard
light micro under pressure
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Command & Conquer: Red Alert
PvP skirmish rewards predicting enemy pushes
Northgard
MP vs adaptive humans
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Command & Conquer: Red Alert
Fog of war conceals army composition
Northgard
winters, wandering events
Command & Conquer: Red Alert leans a little harder on optimization, though the gap is small.
Command & Conquer: Red Alert
Ore economy and build orders decide games
Northgard
clan economy and tile control
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.