Attack damage converted to life

[Natacha Gronlova]

Attack damage converted to life Is it only with physical damage or does it apply to all sources of damage, whether magic or otherwise?

In other words, can a black water cocktail or other constant area damage give me life?

[gNuff!~©~gNom3™]

global/passive lifesteal(attack dmg converted to health) that appears in your char sheet page 2 only works with weapon dmg/skills and effects that lists %WD specifically, dmg type doesn't matter
So no, BWC can't lifesteal because it has no weapon dmg, it would require a modifier that adds direct lifesteal to the skill (iirc that doesn't exist)
On that note, or as it may have alluded to, that is the other type of lifesteal, native/"baked in to a skill", such a skill ofc doesn't require weapon dmg as the lifesteal is directly part of it and will lifesteal based on the flat dmg amount (true DoTs can't lifesteal, burn/poison/bleed etc etc)

[madrigal]

It applies to any weapon damage, and any skill that does partial weapon damage. Spells (including BWC) don't have weapon damage unless you have an item that specifically adds it to the skill. So most spells don't have lifesteal.
There's a dagger, Ugdenbog Flamestrike, that adds flat damage to BWC, but I'm not entirely sure if that counts. I'm sure somebody else will chime in in a minute.

[gNuff!~©~gNom3™]

being a spell is irrelevant, what matters is if the skill has weapon dmg
Forcewave is a spell, Bone Harvest is a spell, Callidor's Tempest, Flames of Ignaffar, these all have default weapon dmg scaling so can scale global/passive lifesteal

Adding flat dmg to a skill doesn't add lifesteal or lifesteal effect, it will only scale additional dmg to the skill to lifesteal from if that skill can lifesteal, be it native lifesteal like Siphon Souls or weapon dmg like Shadow Strike etc "more dmg = more healing"
To add lifesteal effect to a skill it has to be +%weapon dmg specifically that gets added, in which case it can scale global/passive lifesteal, or it has to be a direct lifesteal modifier, like Pulsing Shard for AAR

edit,
wd mod example https://www.grimtools.com/db/items/11359
lifesteal mod example https://www.grimtools.com/db/items/2191

*note global/passive lifesteal is scaled by %wd amount if below 100, so in this case Slathsarr medal would add 30% of char's global/page 2 lifesteal amount (doesn't scale above 100% effect )
direct lifesteal modifiers ofc just applies the listed effect in full/"you get what's written on the label"

[Natacha Gronlova]

One last question.
Which of the two is the most used, life theft or regeneration?

I tried to understand several videos where I see that life is restored but I can't understand them.

The life steal I have does not add up to more than 12% compared to the amount of life regenerated which almost all items have.

[gNuff!~©~gNom3™]

health regen is its own focus/requires build dedication around, heals you X amount every second
Lifesteal is based off your attack dmg, so, theoretically, if you had 10% lifesteal, dealt 100k dmg you'd heal 10k each attack
It's ofc a bit more complicated than that since it depends on where your lifesteal is, ex being if you're relying on weapon attacks or stuff like siphon souls/effects with different or fixed attack rate. (and ofc enemy resist means sheet dmg isn't the same as effective dmg and)

"generally", if you're a weapon attacker lifesteal is the most simple/effective, with the caveat/usual "exception to the rule" type deal where there are some weapon attackers that natively easily get regen too, because either devos can easily be fitted in or the class just has a lot of it, making a mix regen/lifesteal approach easily doable.
Stuff like Avenger set for Warder, or Ember's Calling saboteur means you can easily scale some regen despite being a weapon attacker that still stacks passive lifesteal for your weapon attacks.

a lot of casters or cooldown casters without WD effects usually go regen simply because they have no means to scale lifesteal or can't scale it enough. Ex being Grenado builds generally can't lifesteal on most setups, so doing regen is easier/better
Meanwhile stunjacks can technically get lifesteal, but it may or may not be enough to feel comfy so they might still go regen, or some heal procs.
Or ofc if a skill/spam skill can get lifesteal mods tacked on to it like the AAR pulsing shard example, means you usually don't have to care about regen and just relies on that native skill (and maybe some heal procs), which is in essence then similar to being a spam weapon attacker with global/passive lifesteal

as long as it's a "spamable" attack that can lifesteal, be it from WD and global lifesteal or a lifeteal modifier usually means you can rely on lifesteal by attack dmg+frequency of attacks. If you don't have frequency of attacks or simply can't get lifesteal in attacks, means regen then is probably what you should aim for

*and like with most things you can't just rely on "1" thing, so like, having 0 other lifesteal/regen sources and just trying to rely on ex Bat+Twin Fangs devotion will not carry you alone. Think of it as "a" source of healing in a required stream of sustain.
(By comparison for a weapon attacker you're usually attacking minimum 3x per second if not hitting multiple enemies per swing)