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

Reads · Competitive PvP
The 2011 reboot that returned Mortal Kombat to brutal 2D fighting fundamentals.

Execution · Grand Arena
A tag-team 3D fighter layering team optimization onto Tekken's execution and reads core.
Mortal Kombat leans Reads (Competitive PvP); Tekken Tag Tournament leans Execution (Grand Arena).
Tekken Tag Tournament leans a little harder on execution, though the gap is small.
Mortal Kombat
Combo execution and punish timing
Tekken Tag Tournament
Tag combos and netsu juggles demand precise inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat
Human opponents adapt; conditioning and counter-guessing rule
Tekken Tag Tournament
Tag timing adds another layer of human mind-games
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mortal Kombat
Near-deterministic systems
Tekken Tag Tournament
Open information; nothing hidden between rounds
Tekken Tag Tournament leans a little harder on optimization, though the gap is small.
Mortal Kombat
Frame data and matchup study converge to known answers
Tekken Tag Tournament
Team synergy and tag combo routing are optimizable systems
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.