Which Raven uses Basiliskos better?

+spd

+spd no doubt about it

Depends on how you build them. If LnD seal becomes a thing, then +atk Raven would be the best user by far since he would hit 68/50 attack/speed unbuffed. I’m just waiting for the day.

But for now, speed is the best way to go.

Spd, especially when running refine+fury+desperation set. It is his best combination because fury allows him to get +8/+8 atk/spd for a measly -2/-2 def/res vs. double LnD where he gets +10/+10 atk/spd for -10/-10 def/res. At the very least, he wants to keep his def stat high because he's going to deal with bulky melee units and any mage he initiates on will likely die to him anyway.

With allied buffs, +Atk is the way to go, since you don't want to use more points in speed than you need. This secures very important kills against heavy tanks, especially the two hectors.
If you're worried about high speed matchups, you should only worry about the sword users, and your composition should already have a blue unit to check them.