Bridal Sanaki

-Def ofc. Prioiritze har BEST stats

+atk is very good, but the speed bane is a killer. Take +spd-def.

No brainer, definitely the +SPD/-Def. Your good choices are either a +ATK or a +SPD, obviously you do not want to take a loss in the speed, and the +Spd/-Def could only be more ideal if it were a -HP instead. I'm surprised you had to ask, tbh. As a general rule of thumb, +SPD is pretty much always going to be your best best on units with middling speed, since even 1 speed can be the difference between 1 hit or 2 hits. X*2 will always be better than X+3. +ATK is only your best option on units that simply cannot be expected to double and rely on things like QR, Bold fighter, etc, or on units who naturally have high speed and don't have weapons that multiply off the speed (EG Karla still wants speed because of her weapon, even though she doesn't need it to double).