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

Execution · Competitive PvP
Futuristic large-scale Battlefield where teams besiege flying Titan carriers.

Execution · Competitive PvP
Vietnam-era large-scale multiplayer shooter mixing infantry firefights with helicopters and jungle ambushes.
Battlefield 2142 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 2142
Gunplay, piloting, and Titan boarding need solid mechanics
Battlefield Vietnam
Gunplay, vehicle handling, and helicopter piloting
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 2142
64-player human teams shift fronts and Titan assaults
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 2142
Large maps hide flanks; battle chaos obscures information
Battlefield Vietnam
Spawn waves and vehicle availability shuffle fights
Battlefield 2142 leans a little harder on optimization, though the gap is small.
Battlefield 2142
Unlock paths, squad roles, and Titan strategy reward planning
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.