head to head
Killer Instinct (2013) asks more than Street Fighter X Tekken, and the gap is reads.

Execution · Grand Arena
A combo system built on constant Combo Breaker mind-games that create a unique adaptive read-off at every moment of a combo.

Execution · Grand Arena
A tag-team crossover fighter pitting Street Fighter's cast against Tekken's under Capcom rules.
Killer Instinct (2013) leans Execution (Grand Arena); Street Fighter X Tekken leans Execution (Grand Arena).
Killer Instinct (2013) leans a little harder on execution, though the gap is small.
Killer Instinct (2013)
Shadow counters and Combo Breaker timing demand very precise inputs
Street Fighter X Tekken
Tag combos and juggle timing demand practiced hands
Killer Instinct (2013) leans clearly harder on reads.
Killer Instinct (2013)
Combo Breaker prediction is a pure read-off against an adaptive opponent
Street Fighter X Tekken
Human mixups and tag baits require adaptation
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Killer Instinct (2013)
No RNG; all mechanics are fully visible
Street Fighter X Tekken
Deterministic aside from negligible elements
Killer Instinct (2013) leans a little harder on optimization, though the gap is small.
Killer Instinct (2013)
Instinct activation timing and optimal opener routes are well-studied
Street Fighter X Tekken
Gem loadouts and team synergy add a builder layer
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.