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.

Execution · Competitive PvP
The Source-engine era of Counter-Strike's aim-and-economy tactical formula.

Execution · Grand Arena
Hero shooter with team-up ability synergies.
Counter-Strike: Source leans Execution (Competitive PvP); Marvel Rivals leans Execution (Grand Arena).
Counter-Strike: Source leans a little harder on execution, though the gap is small.
Counter-Strike: Source
Recoil control and crosshair placement decide duels
Marvel Rivals
Hero aim and ability timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Counter-Strike: Source
Outguessing rotations, fakes, and timing of human opponents
Marvel Rivals
Team-fight cooldown trading is prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Counter-Strike: Source
Hidden enemy positions until information is gathered
Marvel Rivals
Map and team comp roll affects
Marvel Rivals leans a little harder on optimization, though the gap is small.
Counter-Strike: Source
Economy rounds, utility lineups, and map control theory
Marvel Rivals
Hero synergies and team-up combos deep
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.