update: i tested the Y variant, and it seems alot more powerful, where the normal one does around 8-10k dmg, the Y did 20k plus dmg

My theory is that the normal one limits ur dmg to only 1.5x normal dmg without crit, and also limits ur crits to only 75% of the enemies. This means that its probably better against stronger opponents but worse against weaker ones. whereas the Y either increases injury or crit by 45%, not sure. Perhaps someone who knows these answers can confirm it

To clarify:

Critical influences your chance to land a critical attack (and vice versa, decreases opponents chance to land crit).

Injury influences how hard you are going to hit with critical attack (and again, when opponent lands a crit on you, how much >less< damage it will cause)

They are in simple words equivalent of critical hit chance and ciritcal hit damage stats of other games.

Regular susano sasuke mystery has fixed 75% crit chance and a fixed 150% crit damage multiplier. Meaning the only way to increase its damage is increase you base damage (tai/nin). It doesnt scale with injury or critical. Mystery +1 behaves the same, except target changes from max 9units from 1 team only, to max 9 units from across 3 teams.

Y susanoo mystery removes fixed parts of mystery and gives +45% BONUS chance to crit chance (critical stat*, see bottom of the post). Fixed critical damage part is removed, making the mystery finally scale with injury stat.

Now how that influences the game. If you have very very low stats, for example you have 40k bp in total across 4 ninjas- fixed injury effectively makes you deal 1.5more damage on crit. If you tried Y mystery, it would most likely deal less damage, as your injury stat isnt really developed yet. However after a certain point*(again, see bottom of the post) injury stat starts to make you deal more than 1.5x of you base damage on crits. Currently when my pos1 non-crits its in range of 10k, when it crits it sometimes hits 30k on the same target. So my injury (or crit dmg multiplier) is 300%. Thats why Y mystery for sus sasuke is a must for everybody that wants to use him and not be frustrated, that he doesnt deal dmg.

*how exactly stats are calculated, dont ask me. Nobody knows for sure how stats work in this game as there literally never was given a formula for dmg or defense in general. We have rough idea, but thats it.