Which Shigure to sacrifice?

Depends on what you're wanting, and what team you're putting him on.

-Atk +Spd Shigure has 30 attack and 40 speed and +Res -HP has 33 attack and 37 speed.

If you're going with Flier Emblem with Hone Fliers, then I'd say to go with +Spd -Atk Shigure with Firesweep Lance+ and Life and Death 3 hits 50 attack and 45 speed. Throw in Hone Fliers, and he'll hit 56 attack and 51 speed. Galeforce? Throw in Heavy Blade for faster special activation.

Just one of the things you could do with him. Of course, that set could work with +Res -HP Shigure so you won't have the attack bane.