[underdeserver]

This is explicitly addressed:

  When multiple moves have the top score, they are all top moves,

[robertlagrant]

I wonder if a move that checkmates is scored lower than a move that checkmates and captures.

[ht85]

Forced mates are generally scored with the number of moves to mate, e.g. "M2"

[rocqua]

So you can start down a sequence that gives check-mate, but once it is the shortest sequence to check-mate, you have to abandon the check-mate.

[Scarblac]

So you can never actually play a mate in one.

[_dain_]

Checkmate .. with advantage!