Deathwing!

[u]Taken[/u]- Beings granted their [i]"final shape",[/i] their [i]"knife"[/i] by Oryx and the Deep. Because of this, those that are Taken have abilities that compensate for their shortcomings. For example: a vandal must watch itself at all times. Maybe another vandal takes his share of ether, or he slips up and is turned back into a dreg. A vandal has no "safe place" among his House. So, Oryx granted them a deployable shield "a safe place" for Vandals. On the other hand, they are bound by Oryx and his will. Once they are Taken, once they have their [i]"final shape"[/i], they lose free thought. This is a major issue, because once Oryx is dead and no one takes the throne via [i]"Sword Logic"[/i], the Taken are left to age and decay. [u]SIVA[/u]- Are a nanotechnology that can self-replicate-- rather slowly without Replication Chambers-- and build nearly any device if given the proper Directive. They have their own power source, so that isn't a problem either. For example: SIVA could be used to build bases and ships. Weapons from firearms to potential WMD's. Even EMPs are possible as we see a minor version throughout the raid. The problem is if The Director (as I call whoever controls SIVA) dies, and no one else knows the proper protocol, SIVA will relentlessly continue to fill out their last Directive. Which we know is ~consume, enhance, replicate~. Because of this, if this Directive stands and nothing else, SIVA will continue to consume material (~consume~), enhance its overall technological abilities (~enhance~), and will continue to duplicate itself (~replicate~). This can be a bad thing, especially if you wanted to rebuild a grand city, a new Golden Age, but something stops you, the Director, were stopped from changing SIVA's Directive. Personally, I lean to SIVA being the worse from the two.

If you think about it, both SIVA and the Taken are similar (not the entities themselves, but the power behind it). Both act similar to a disease; both take over their hosts (consume), both give them enhanced abilities (enhance), and both spread (replicate). The only difference is that we see more variety with the Taken. We see it infect all the known enemies in Destiny. The SIVA only affect the Fallen, because only the Fallen are exposed/have access to it. But also remember that the Splicers tried infusing SIVA with the Hive. Shiro himself said, "...it could mean the end of everything." The end of the City. The End of the Traveler. The end of Light itself. The Taken do not show such potential. While it spread like a stain across the Solar System, that stain [i]could [/i] be cleaned up. Especially after we killed Oryx. This implies that, while Oryx had millions of years to master its power, it was limited. SIVA can infect Guardians! Something the Taken blight could never accomplish, because of our Light. The only reason SIVA isn't more devastating is because the Fallen have an incomplete understanding of it. "Like children with a new toy", as Saladin puts it. To answer the question, "Is SIVA or the Taken deadlier?", I must answer, "SIVA." Because while the Taken belongs to Darkness, we can fight the Darkness. SIVA is a failure of our past. And the past will always come back to haunt us.

Siva because since it doesn't have a will of it's own it is as evil as the person controlling it and there could be plenty of ways to get creative with it

The taken are way more dangerous because when are enemies get taken, they gained new powerful powers, like creating an Acolyte's Eye. When the fallen got siva infected, they just got a slight change in their skin and shape.

The taken were -blam!-ing scarey first time. Siva, not so much.

If we're talking about more deadly to our Guardians, then most definently the Taken. They're the closest thing to the Darkness that we've encountered thus far. Combine that with the powers of the Ascendant Hive and the Ascendant Realm, and they are an infestation that can consume planets. In fact, even after Oryx had been killed, the Vanguard was still fighting the Taken War. If we're talking about the potential to be more threatening, I'd say SIVA. As we know, SIVA can infest the environment, as well as manipulate technology and even Guardians' armor. Additionally, even with the Splicers' very limited knowledge of how to manipulate SIVA, they still managed to resurrect their Prime Servitor and ascend Aksis to near-godhood. Imagine what it could do in the right hands.

Taken is a corruption and SIVA is a mere technology.

I think SIVA is more deadlier than taken for some reason but my vote goes to taken. My reasons for SIVA is when a directive is enter like Rasputin entering consume, Enhance, Replicate for killing the iron lords, it won't stop unless a new directive is put in which is my opinion should of been the end game mission where we enter a new directive. Why my vote goes to Taken is because you are a easy target and when taken, you are dead because you are tortured by Oryx, then your body is rendered for citing for the ships and when killed as taken, your soul doesn't go to your original body. But instead of my vote to Taken, SIVA wins.

When you consider the lore, the Taken.

Never felt like Siva were a threat. Compare that to the black spindle mission.. case closed

Taken. SIVA (ROI) was just a filler to "hold" us off till destiny 2. Destiny 2 raid boss or race has to be more powerful than oryx and the taken.