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 · Practiced Mastery
Prequel chronicling Noble Team's doomed defence, with armour abilities reshaping multiplayer.

Execution · Competitive PvP
Stick-skill football execution with opponent prediction in versus play.
Halo: Reach leans Execution (Practiced Mastery); UEFA Euro 2008 leans Execution (Competitive PvP).
Halo: Reach leans a little harder on execution, though the gap is small.
Halo: Reach
DMR precision and armour-ability timing
UEFA Euro 2008
Pass timing, dribbling and finishing decide matches
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Halo: Reach
Multiplayer rewards predicting human movement
UEFA Euro 2008
Versus humans, baiting tackles and disguising attacks matters
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Halo: Reach
Loadouts and spawns add small swings
UEFA Euro 2008
Bounces and deflections add football's usual noise
Halo: Reach leans a little harder on optimization, though the gap is small.
Halo: Reach
Ability matchups and map knowledge
UEFA Euro 2008
Formations and squad selection sit underneath
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.