Surprise attack much better. It scales with M-A-A, passively gives u hp, procs shadow barrier. Flurry doesnt proc a bleed from axe because it is a channel. Surprise attack applies also Major Fracture, it is also instant what is more comfortable to use in rotation. Can proc Selenes, Flurry can't. I think enough.
I come into the thread and be hopefully for any answers i actually miss.. then i use see a question between 2 skills from 1 class..
Pls just test both on a dummy with same setup. This will give you an answer for this and all other kind of questions like that...
AND pls dont make a thread for every skill...