My first thought is to question the 1-1 Claydol, because I am so used to 2-2 Claydol. BUT, I run a 1-1 Claydol in my Regigigas and it works brilliantly...i mean, I always get it out, which is funny. I guess with Azelf in here, having a piece prized is not as harmful.
Just noticed that the Promo Dusknoir has 10 more HP than both the SF Dusknoirs. Neat.
How does Dusknoir get around Unown G? If we compare the attacks of all the Dusknoirs, we see a lot of attacks that work with damage counters and those don't affect Unown G'd Pokemon. So that means that SF #1 Dusknoir is a pretty bad attacker with Unown G on key Pokemon. That means that DP Dusknoir is useless as an attacker. That leaves the Promo one and the SF #17 Dusknoir. The Promo Dusknoir move damage counters off itself. Although you wouldn't be able to move the damage counters onto a Unown G'd Pokemon, you could still move it onto something else that isn't Unown G'd. So his attack isn't totally invalidated. SF #17 Dusknoir's attack doesn't apply effects of attacks like damage counters, and thus isn't affected by the opponent's use of Unown G at all. I think it is important that every Dusknoir deck needs to have 1 of these 2 Dusknoir in them just so they have a decent attacking option against Unown G heavy decks.
But each player has to weigh the advantages and disadvantages of both of them. The Promo one can possibly remove a Pokemon from the opponent's hand, which can be very useful. The SF Rare Dusknoir can spread damage on all the opponent's Pokemon that have energy on them. The Promo one seems like it would be able to survive longer than the SF Rare because of it's 10 more HP and ability to move 2 damage counters off of it.
How much more survivability does the Promo Dusknoir have? 4 shots of 50 will knock it out (50-20 = 30 + 50 - 20 = 60 + 50 - 20 = 90 + 50 for KO). Normally, just 3 shots are needed. This changes at 60 damage, but is still in Promo Dusknoir's favor since it has 10 more HP than the other Dusknoirs and can survive 1 more attack because of it. The extra 10 HP also allows it to survive 2 shots of 70 (70-20 = 50 + 70 = 120). Any damage higher than 70, and the extra HP AND the effect of the attack does nothing to help it survive longer.
So, the question really comes down to what kind of damage do you see being done at tournaments? Against Kingdra, the Promo Dusknoir would be able to survive better than the other Dusknoirs, but that isn't totally correct. The SF #1 Dusknoir's second attack, Night Spin, pretty much wins you any Kingdra matchup. So, really, against Kingdra, the Promo Dusknoir's survivability isn't that important. Every other deck does more than 60 damage on average. Regigigas does 100 damage, which is the magical 80 after resistance, which is enough to totally invalidate the Promo Dusknoir's extra HP and removal of damage. Tyranitar is probably gonna do 80 or more or just OHKO you. The Promo Dusknoir's extra HP and removal of damage might help against Mirror matches, since Dusknoirs in general don't do massive regular damage, and an Unown G on the Promo Dusknoir makes it unaffected by damage counter snipe-age. Scizor is going to be pumping out at least 70, most likely 80 or more, so again, the extra HP and removing damage doesn't help much in that matchup. Against Abomasnow, the moving 2 damage counters could help some, as you'd be reversing some of their spread in the process, but it won't help tremendously as they never mean to OHKO or do MASSIVE damage to your active Dusknoir.
So, in many matchups, the extra HP and damage removal (or transfer) doesn't help tremendously, but it's Poke-Power is still very decent and it's attack is one of the few Dusknoir attacks that isn't totally nerfed by Unown G. Let's look at the SF #17 Dusknoir and see if it's worth playing over the Promo one.
So, the SF #17 Dusknoir brings 2 qualities to the game. It's Poke-Body can spread damage on things that have Energy on them, and it's attack can do 80 damage if the defending Pokemon has 2 or more damage counters on them. Sounds like a perfect pair of ability and attack, right? Definitely, if your Dusknoir deck is focused more on spreading small amounts of damage all over the place instead of big whopping hits of damage counters on key critters, then this Dusknoir would be right up your alley.
I do wonder how useful it's Poke-Body is, though. How do the Popular decks lay their energy on the field, and could SF #17 Dusknoir's Poke-Body really spread that well. Looking at the same decks (regigigas, tyranitar, mirror, kingdra, scizor, and abomasnow), Regigigas only tend to attack to key Pokemon like Regigigas, so there doesn't seem a big chance to spread there. Kingdra can get away with no energy on them, because all they need is 1 energy to use their second attack and no energy whatsoever for their first attack. I think most of these decks don't really spread energy all over the board. So, it seems that Poke-Body on the SF #17 Dusknoir will usually just damage the main attackers. That's not a bad thing, though. It just means that it won't work as super well with Bronzong laying extra damage on Key Poke-Powered Pokemon like Claydol.
In the end, I don't know if I prefer one over the other. If you like Disruption more than Spread, then I would say use the Promo Dusknoir, but if you want your Dusknoir deck to be 100% spread, then I guess the SF #17 Dusknoir is your man. Neither are a bad choice but neither really bump the other out of the view and make you want to play them over the other.
I think the DP Dusknoir is a staple. Someone asked earlier, "what if you don't play it?". What happens is that the opponent assumes you are playing it, and keeps their bench to 3 or less, and then when they figure out your not running it, fills their bench. This helps some decks more than others. Decks like Kingdra that abuse multiple Uxie and Mesprit (Regigigas), really need that bench space, especially if you don't KO their starting Sableye/Chatot/etc. Other decks, like Scizor, don't need the bench space as much. 2 Scizor, 2 Cherrim, and they are still putting out 90 damage a turn, which is great. Right now, though, I feel it's important to run the DP Dusknoir because the opponent's bench space is precious with the Pixies and more complicated decks needing helping helpers like Weavile. In those cases, you are in a situation where you can gain something by disrupting their field.
So, this is how I see the Dusknoir layout. You gotta have 1 DP Dusknoir, period. You gotta have 1 SF #1 Dusknoir. If not for it's sweet Poke-Power, it's super snipe attack, and it's Kingdra-winning second attack. Let's say for the matter of this discussion that we are using the Lv.X, so that is 3 slots so far filled. From there, as much as I'd want to play another SF #1 Dusknoir, in a field with a lot of Unown G, I think the better bet is the Promo Dusknoir or the SF #17 Dusknoir.
