I'm currently discussing Kayns forms with a friend and they believe Shadow Assassin trumps Darkin in almost every aspect. But my counter-argument is that Rhaast is a far better teamfighter and has much more survivability even if you get caught out.
Which form is better? I really don't know the winrate difference and other than my points, I can't think of much else. I've played both and I prefer Darkin much more than Shadow Assassin.
nm10102 votesThere are very few times SA does something Darkin can't do, Darkin does many things SA can't do.
Mighty Mortein1 votesThere are very few times SA does something Darkin can't due, Darkin does many things SA can't do.
I know SA makes up in the damage department because of the magic damage passive, but that only accounts for 3 seconds after entering combat. Rhaast's healing passive applies throughout every second he can pump out an ability.
dolphinosplash241 votesRhaast is better is most situations
Escheton1 votesDepends on the situation. SA blows up backline better if he can get a flank or pick. Rhaast deals with front line better. How do you wanna come at them? Usually depends on team comp and who is fed. Or personal affinity.
Friendly Ram1 votesrhaast is a better all rounder whil assassin form is better at assassinating people but really can't teamfight.
warpenguin5551 votesRhaast 100%. CC and Healing > more damage
The Deckowner1 votesWhen in doubt, well you shouldn't be in doubt because red Kayn is obviously neyter, but just pick red kayn anyways.
Ironfield1 votesIf youre snowballing and can end the game early go Shadow assassin to push your win condition, if no go for the more reliable team fight presence with raast.
edit: Also depends on there team comp, if they consists of no tanks then going shadow assassin my be more beneficial do to Raast having more %HP damage compared to the higher flat damage of shadow assassin