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 · Practiced Mastery
Classic RTS that polished Warcraft's formula with naval combat, air units and beloved multiplayer.
Command & Conquer: Red Alert leans Optimization (Pure Optimization); Warcraft II: Tides of Darkness leans Optimization (Practiced Mastery).
Warcraft II: Tides of Darkness leans a little harder on execution, though the gap is small.
Command & Conquer: Red Alert
Micro and base management under time pressure
Warcraft II: Tides of Darkness
Faster micro across land, sea and air units
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
Warcraft II: Tides of Darkness
Multiplayer scouting wars and build feints
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
Warcraft II: Tides of Darkness
Fog of war conceals enemy tech and armies
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
Warcraft II: Tides of Darkness
Refined build orders and upgrade timings are studyable
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.