Okay so I thought about this earlier today while driving my car, totally random at that, but anyways, so I was thinking, what is the main difference with lifesteal and spell vamp?
I mean aside the obvious of Spell Vamp only working with abilities, but what I want to know is, is Lifesteal only for basic attacks, or all around damage?
Do they stack? As in a 12% LS and a 20% SV = 12% LS and 32% SV.
I haven't seen this discussed so I thought it'd be some good info to have.
No, some abilities have effects that trigger on hit effects, like 
's Q which will proc Lifesteal, but Lifesteal wont proc on his ultimate at all. Only Spellvamp will.
To make this easeir to understand.
Lifesteal Triggers on Auto Attacks and Abilites that proc On-Hit effects.
Spellvamp Triggers on Ablites only.
However, I am uncertain as to whether something like Ez's Q while Knowingly proc'ing Lifesteal, will also proc Spellvamp, because at its heart it is an ability.
Believe it or not, the answer is no, they do not stack. Usually any ability with on-hit effects (the only type where LS or SV could have the opportunity to stack) are meant to never effect spell vamp or Rylai's slow. This prevents abuse for obvious reasons.
