Which presence is best for pvp?

In case some of you are still wondering, I've already been through this argument here. :)

Q u o t e:
If we stick to the target we can BS/BB and RP dump and repeat.

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This is key. I underlined the most important word in that sentence.

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Q u o t e:
Blood presence = more damage

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This is only true if you can stick to the target for the vast majority of the fight.

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Q u o t e:
Blood presence = bigger burst

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Actually, unholy presence is. You even already outlined how and why:

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Q u o t e:
Unholy presence - 1 GCD
IT or Chains - 1 second
Plague Strike - 2 seconds
SS/Obliterate - 3 seconds

Blood presence - 1.5 GCD
IT or Chains - 1.5
Plague Strike - 3.0
SS/Obliterate - 4.5

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Your auto attack damage is the same, since 15% more auto attack damage = 15% faster auto attack speed. Your specials are doing 15% more damage in blood presence, yes. However, you are spending your runes and doing specials 33% faster (which yields a bigger burst potential).

Let's use your own example, using some static numbers. And let's also assume that you don't even need to use chains, and you're not getting kited, which plays in favor of blood presence.

Blood presence:

IT = 575 damage (500 *1.15)
Plague strike = 575 damage (500 *1.15)
Obliterate = 1150 damage (1000 * 1.15) = 2300 damage in 4.5s This is a burst DPS of 511.

versus

Unholy presence:

IT = 500 damage
Plague strike = 500 damage
Obliterate = 1000 damage = 2000 damage in 3s. This is a burst DPS of 666.

Again, auto attack damage per second (not damage per hit) is the same, so it's a nil factor.
Once you factor in that as a melee class, you will spend a considerable amount of time chasing the target, the fact that unholy presence also offers a tool to aide in this by providing a 15% run speed tips it more in the favor of being the pvp presence.

Unholy presence is better burst damage in pvp, and better mobility. Not to mention, there also is the intangible bonus of being much less likely caught in GCD when you need to hit IBF, bone armor, or strangulate. It has defensive purposes as well, in this light, that blood presence cannot provide, due to the GCD barrier.

Edit: Fixed Math Errors.