I think the key here is Lethal damage. Claws and Ninja Blade both do lethal - the one type of damage that is most resisted by players and mobs alike.
Spines has Lethal/Toxic, EM has Smash/Energy. Toxic is a killer as there is so few resists/defences for it, and energy while commonly resisted is never to the same level as Smash/Lethal.
Still, I've seen Blade/* Stalkers getting kills in Sirens, so it isn't a lost cause 
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Still, I've seen Blade/* Stalkers getting kills in Sirens, so it isn't a lost cause
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You couln't see me then... I'm on Union. 
On a more positive note, the AS damage can't be resisted in PvP, so it doesn't matter what you use for that, and the ninja blade has a small accuracy bonus.
It CAN be resisted in PvE, thus I found it much easier to AS CoT ghosts and Freakshow Tanks with my EN stalker than my ninja blade stalker. (And the animations are shorter, cos you don't have to pull the damn blade every time you use a power from the secondary set! 
)
I'm a Claws Stalker and I have a happy time of it. Claws has focus the the only other ranged move available other than Impale. Focus is very useful and with Build up or from Hide I can happily knock 50% of the health of a Controller or Defender type and more often than not bring down a runner as well. Quite happy with the damage overrall and due to my lack of stealth I find myself fighting out in the open a lot more than you should with a stalker and it serves me well. As for Ninka Blade, Dark Figment is specced along those lines and he seems to be quite happy with it as well as quite successfull. Only gripe he has is the lack of a ranged ability which is quite a drag, I know I rely on mine a lot.
I'm a Claws Stalker and I have a happy time of it. Claws has focus the the only other ranged move available other than Impale. Focus is very useful and with Build up or from Hide I can happily knock 50% of the health of a Controller or Defender type and more often than not bring down a runner as well. Quite happy with the damage overrall and due to my lack of stealth I find myself fighting out in the open a lot more than you should with a stalker and it serves me well. As for Ninja Blade, Dark Figment is specced along those lines and he seems to be quite happy with it as well as quite successful. Only gripe he has is the lack of a ranged ability which is quite a drag, I know I rely on mine a lot.
any type will do if you wanna take down the squishies fast, however if you try to take down tanks or scrappers EM and Spines would be better yeah. Spines because of the toxic damage (and minor debuff) and EM.. well.. it's all about the toggledrops baby. If I play my tank in PvP, from all stalkers EM stalkers are most hated by me.
"god, how many devs did hami have to sleep with to get ED?"
Total Cat @Stagefright
Several ppl have said to me...
"Its a cool ninja blade you got there, but damn its useless in PvP compared to other stalker types"
Is it true, heard the best would be either spines, because of impale, or Energi because of a insanely high dps and the stun effects... Also ive noticed that my ninja blade dont give as much dmg as i had hoped for.. (still waiting to get soaring dragon tho xD) but what about claws, they are damn fast.. dont they have a very high dps aswell? and martial arts.. i hardly see anyone use em why not ??!!