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

Execution · Competitive PvP
WWI conquest shooter with weighty gunplay.

Execution · Competitive PvP
Vietnam-era large-scale multiplayer shooter mixing infantry firefights with helicopters and jungle ambushes.
Battlefield 1 leans Execution (Competitive PvP); Battlefield Vietnam leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 1
Bolt-actions reward steady aim and timing
Battlefield Vietnam
Gunplay, vehicle handling, and helicopter piloting
Battlefield 1 leans a little harder on reads, though the gap is small.
Battlefield 1
Trench flanks and gas plays beat predictions
Battlefield Vietnam
Human squads flank and contest objectives unpredictably
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 1
Behemoth spawns and chaos shift matches
Battlefield Vietnam
Spawn waves and vehicle availability shuffle fights
Battlefield 1 leans a little harder on optimization, though the gap is small.
Battlefield 1
Class kits and vehicle counters matter
Battlefield Vietnam
Map control, loadouts, and ticket-bleed knowledge
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.