head to head
vs
Left 4 DeadvsUntil You Fall
Left 4 Dead leans Execution (Twitch Chaos); Until You Fall leans Execution (Practiced Mastery).
Left 4 DeadUntil You Fall
Axis by axis
Execution7 vs 7
Even - both lean on execution about the same.
Reads2 vs 1
Left 4 Dead leans harder on reads: Versus mode adds human ambush mindgames
Variance5 vs 4
Left 4 Dead leans harder on variance: AI Director randomizes hordes, items, and specials
Optimization5 vs 5
Even - both lean on optimization about the same.
Two games can score the same on an axis and still test it in very different ways - read each rationale, not just the number.