head to head
Neither is simply harder - they are hard in different places. Eisei Meijin VI demands more reads; Spy vs Spy demands more execution.

Reads · Pure Mind Games
A Japanese shogi (Japanese chess) simulation game.

Reads · Pure Mind Games
A split-screen trap duel testing prediction of where your human rival hid the bombs.
Eisei Meijin VI leans Reads (Pure Mind Games); Spy vs Spy leans Reads (Pure Mind Games).
Spy vs Spy leans clearly harder on execution.
Eisei Meijin VI
no physical input skill, purely turn-based
Spy vs Spy
Simple movement and item fiddling under time pressure
Eisei Meijin VI leans clearly harder on reads.
Eisei Meijin VI
shogi opponents genuinely adapt to your play
Spy vs Spy
Guessing where the rival spy laid traps is the core duel
Spy vs Spy leans clearly harder on variance.
Eisei Meijin VI
no hidden information or randomness at all
Spy vs Spy
Item locations are hidden information each round
Eisei Meijin VI leans a little harder on optimization, though the gap is small.
Eisei Meijin VI
deep opening/endgame theory to master
Spy vs Spy
Trap-and-counter knowledge forms a learnable 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.