head to head
Tetr.io asks more than Tetris Effect: Connected, and the gap is reads.

Execution · Pure Mechanics
A competitive online stacker testing raw speed and versus stacking strategy.

Execution · Pure Mechanics
The classic execution-under-acceleration test wrapped in an immersive audiovisual experience.
Tetr.io leans Execution (Pure Mechanics); Tetris Effect: Connected leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Tetr.io
Lightning-fast piece placement decides every match
Tetris Effect: Connected
Precision placement under acceleration is the entire skill ceiling
Tetr.io leans clearly harder on reads.
Tetr.io
Human opponents in versus can be anticipated somewhat
Tetris Effect: Connected
Zone-battle opponents exist but format leans on execution
Tetris Effect: Connected leans a little harder on variance, though the gap is small.
Tetr.io
Bag randomizer is bounded and quickly mappable
Tetris Effect: Connected
Piece bag is bounded random but quickly mappable
Tetr.io leans a little harder on optimization, though the gap is small.
Tetr.io
Stacking and garbage-management strategy underneath the speed
Tetris Effect: Connected
T-spin and stacking strategy is knowable but execution overrides it
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.