First, Usopp and Sogeking are the same, so why make the lame argument they use different weapons? Second, look a these pics.
You wouldn't stoop to insulting the idea if you did not recognize the merit in it; it's obvious for anyone to see that the Impact Dial is so rare it's a signature weapon of Usopp, so he wouldn't use it in battle under any circumstances while acting under the Sogeking persona.
I'm not looking at any of your "evidence" because I know factually that Sogeking and Usopp never used weapons of their alternate personas; by making the inference that Sogeking would use the Impact Dial, you are stepping into speculation and therefore have the high potential of being wrong.
In these scenes, we see Krieg has to prepare the battle spear, not just pull it out his ass. On a similar note, Krieg usually doesn't use it until he knows he might loose. The crew even said "Look, his deadliest weapon!" like they don't get too see it too often. Sogeking, on the other hand, would have Kabuto out from the begining.
Firstly, I think your knowledge of the manga is a bit weak if you're actually telling me Krieg thought for any moment during his battle with Luffy that he was going to lose. Additionally, however long it takes Krieg to prepare the spear does not matter all that much since Sogeking effectively do enough damage to knock him or or kill him while he prepares it, given that Sogeking must be at close range for Krieg to actually warrant pulling out the spear.
In any matter, Krieg could just as easily punch Sogeking with his diamond-studded fist as whip out his spear; given how fragile Sogeking is, that wouldn't outright kill him but would cause immeasurable and probably debilitating damage.
Both Krieg's actions and the comments from the cutthroats prove you have to put a "swing" into the spear in order for it to be effective. And Luffy proved it can be broken. Also, Sogeking has the caltrop stars which would pevent Krieg from getting close (At least, with irritation).
Sogeking is considerably more agile than Luffy, but he's not immune to the splash damage of the explosion from Krieg's spear. Give what we've seen of Usopp in the Mr.4 fight, Sogeking has a high tolerance for surviving explosions but he most likely wouldn't be able to take too many hits from Krieg.
However, remember that such is only Krieg's melee weapon, and he has a number of interesting gadgets that could just as easily waste Sogeking from a close or moderate distance, as I said earlier.