Building comparison
head to head
DayZvsH1Z1
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.
DayZ
Variance · Grand Arena
Hardcore survival sandbox where other players are scarier than the zombies.
H1Z1
Execution · Grand Arena
Early battle royale where scavenged loot and shrinking gas decide 150-player brawls.
DayZ leans Variance (Grand Arena); H1Z1 leans Execution (Grand Arena).
DayZH1Z1
Axis by axis
Execution6 vs 7
H1Z1 leans a little harder on execution, though the gap is small.
DayZ
gunfights punish slow hands severely
H1Z1
Gunfights and vehicle control decide duels
Reads6 vs 6
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
DayZ
every survivor met may lie, ambush, or befriend
H1Z1
Outguessing human rotations and pushes
Variance7 vs 6
DayZ leans a little harder on variance, though the gap is small.
DayZ
loot spawns and who you meet are unknowable
H1Z1
Loot spawns and gas circles randomise runs
Optimization5 vs 4
DayZ leans a little harder on optimization, though the gap is small.
DayZ
map knowledge and survival routines compound
H1Z1
Drop spots, loot routes, and zone play
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.