BotRK

Effects:

+25 attack damage
+15% life steal
+40% attack speed
Passive Unique: Your attacks deal 5% of the target's current health in physical damage (60 max vs minions and monsters).
Active Unique: Drains target champion, dealing 15% of the champion's maximum Health in physical damage and healing you by the same amount. Additionally you steal 30% of their movement speed for 4 seconds - 60 second cooldown. (500 range)

Cost: 3200g

VS.

Effects:

+70 attack damage
+12% life steal
Passive: Gain +1 attack damage and +0.2% life steal per kill (maximum +30 attack damage and +6% life steal). Half of the bonuses are lost upon death.

Cost: 3200g

What is better for what situations, and when should you build BT instead of BotRK and Vice Versa. Which provides more lifesteal, the only variable being the stats of the weapon?

I find myself constantly questioning my decision on which weapon to get and would really love some in depth answers. Would be great if any examples given were given from the ADC side of the house.

3 Answers

Initial Thoughts

It seems like BT is the best choice if you look at it fully charged. But I'm not sure. In terms of lifesteal - healing the BotRK returns half of the damage from its passive back.

Which means (very simplistically) that to a champion with 2k health (which is pretty medium) and NOT taking into consideration the armor (I will do the same for BT thats why I say simplistically) it deals 80 damage and you heal for 40.

The extra lifesteal of a FULLY charged BT is 8%. So that being said IF you have 400 damage (which is a lot) and the opponent has no armor you will deal 400 damage and heal for 32.

So the way I see it in terms of lifesteal, BT might actually be worse. It's also definitely more expensive and its also a kind of snowball item so its risky. You will most likely not have it fully charged the whole game.

In terms of actual damage for the same opponent of 2k health and no armor (lol)
You will get a bonus 70 damage per hit with BT and a bonus of 80 damage per hit with the Ruined King. Of course the lower health the opponent the lower the effect of Ruined King.

The only aspect that gives BloodThirster an Edge (in my opinion) is critical damage and skills that scale with AD.

When you crit that extra 70 damage I mentioned above becomes 140. The on hit effect damage from Ruined King can't crit. So if you have an Infinity's edge and a phantom dancer or Trinity Force maybe late game Bloodthirster will definitely give you more damage. (Unless you got a mundo with 4k health there.)

As far as skills are concerned it's pretty straightforward that BT gives you more flat AD so it boosts your spells more than Ruined King.

And don't forget you get the active from Ruined King too.

Final Thoughts

I totally forgot the fact that its nothing like Madred's. It uses CURRENT health not maximum. So as you can see if you have a champion with current health less than 1500. You deal less damage than BT and I'm pretty sure you're gonna heal for less as well.

That being said in combination with everything I said above, I'd go with Ruined King only with opponents that have a maximum health of over 3k.

Outside Link: Here you can find specific numbers which pretty much draw the picture of this duel

Post Patch 3.03 Thoughts

They now changed the item as follows:

Stats +25 attack damage +15% life steal +40% attack speed Passive Unique: Your attacks deal 5% of the target's current health in physical damage (60 max vs minions and monsters). Active Unique: Drains target champion, dealing 15% of the champion's maximum Health in physical damage and healing you by the same amount. Additionally you steal 30% of their movement speed for 4 seconds - 60 second cooldown. (500 range)

I like these changes a lot mainly because it no longer gets shadowed by Bloodthirster. Its now an item for a completely different purpose. If you want attack damage with your lifesteal the choice is even clearer now - Bloodthirster. But if you want the extra attack speed and an (even better than before) on hit effect against health tanks Blade of ruined King is your clear choice. By making this item more unique I consider this a buff.

As a sidenote: After they took out Mardred's On-Hit-Effect Tanky Teemo (Malady, Wits End, Frozen Mallet, Mardred's) was seriously hit. With this item this build is back in town (not as good as it used to be with Mardred's but still its nice to have the option to play it)

Which provides more lifesteal, the only variable being the stats of the weapon?

This is impossible to answer, since BotRK does damage based on your opponents health. Genrally, BotRK will heal more when attacking champions because of their high health but BT is better for sustain from minions or jungle mobs.

What is better for what situations, and when should you build BT instead of BotRK and Vice Versa.

Because BT provides more AD (70-100 vs 40), it's going to perform best on champions with skills based on AD. Consider Riven, who's every ability scales on AD. The extra 60 AD she can get from BT is amplified by each ability, making it a clearly superior choice.

Alternatively, champions who benefit from attack speed will do more damage with BotrK's passive. Teemo is a good example of an attack speed champion who's skills don't rely on AD.

BotRK provides an active that deals damage, heals your champion, and slows your opponent. This is a great ability in general, and is especially useful on champions without slows/stuns. BotRK will also deal more damage to high health targets, and combos well with Last Whisper to shred through tanks.

tl;dr Pick BloodThirster for champions with AD based skills and Blade of the Ruined King for attack speed or on-hit champions. BotRK is also very good at shredding tanks.

As has been discussed in other answers, BT has the advantage that its damage goes into critical damage calculations. This means that it works well with items like Infinity Edge and Phantom Dancer. This means that it is usually superior on AD carries, who will have those items.

BotRK tends to be built more on champions that only build 1 (or maybe 2) offensive items - it might not synergize with other offensive items very well, but it is strong as a single offensive item. This usually means bruisers who come out of top lane or jungle (especially jungle since jungle has a harder time charging BT usually). Such bruisers usually get the most use out of the active too - they love the ability to have another gap closer from BotRK's active.

Therefore, I recommend that you built BT on AD carries and BotRK (sometimes) on bruisers. There will likely be exceptions (if you play against a lot of high HP champions, it might be worth it to build BotRK late on ADCs), but the general rule of thumb is pretty clear.