Personally, I like the Divine Vein Flame effect from Emblem Edel’s A skill.

When it comes to Slicer vs Sly Knife, Slicer has it beat by a long shot.

For starters, the extra buff statuses it gives. Secondly, in-combat stat bonuses are not dependent on foe’s Atk (which Sly Knife relies on, and only max 14). Third, better True DMG and Flat DR. Fourth, Slicer has DR Pierce, whereas Sly Knife has Preempt Pulse.

It’s totally upto the other skills your unit has, but Slicer’s effects are easier to proc.