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 · Grand Arena
The genre-defining historical RTS, still alive on the ladder.

Reads · Grand Arena
Cold-War base-builder where tight production queues and superweapon races define competitive play.
Age of Empires II: Definitive Edition leans Optimization (Grand Arena); Command & Conquer: Red Alert 2 leans Reads (Grand Arena).
Age of Empires II: Definitive Edition leans a little harder on execution, though the gap is small.
Age of Empires II: Definitive Edition
micro and macro APM at high ladder
Command & Conquer: Red Alert 2
Superweapon timing and unit grouping require practiced multitasking
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Age of Empires II: Definitive Edition
PvP ladder rewards adaptation
Command & Conquer: Red Alert 2
Opponent faction and rush timing must be scouted and predicted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Age of Empires II: Definitive Edition
random map spawns minor
Command & Conquer: Red Alert 2
Map layout is fixed; very little hidden RNG in unit behavior
Age of Empires II: Definitive Edition leans a little harder on optimization, though the gap is small.
Age of Empires II: Definitive Edition
civ build orders deeply mapped
Command & Conquer: Red Alert 2
Build queues and power grid management are highly optimizable
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.