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
Out-executing and out-predicting another human in frame-precise duels.

Execution · Grand Arena
A tag-team 3D fighter layering team optimization onto Tekken's execution and reads core.
Super Street Fighter IV: 3D Edition leans Execution (Competitive PvP); Tekken Tag Tournament leans Execution (Grand Arena).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Super Street Fighter IV: 3D Edition
Links, anti-airs and motion inputs gate every level of play
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.
Super Street Fighter IV: 3D Edition
Footsies and conditioning a human opponent decide matches
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.
Super Street Fighter IV: 3D Edition
Almost fully deterministic once inputs land
Tekken Tag Tournament
Open information; nothing hidden between rounds
Tekken Tag Tournament leans a little harder on optimization, though the gap is small.
Super Street Fighter IV: 3D Edition
Frame data, matchup knowledge and punish routes underpin everything
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.