Both phantom and Vertex have the ability not to interfere with accuracy unlike the bird cage hider, to improve accuracy is first claimed by the manufacture, and later confirmed by PK of SAR in one of his awesome article.
I use both the phantom and also the vertex, my phantom equipped SPR rifle I have got 1/4MOA with TAP at 100yards. I had the rifle with out hider at first, I got a good 1/2 MOA consistently at 100, then I had my smith tap and thread on the Phantom, the group remain at 1/2 MOA consistently, but I occasionally have a group down to 1/4MOA. again, this doesn't mean anything, because I could be getting better as a shooter(what a joke :)), but I think the Phantom definitely do not diminish the accuracy on a rifle. and that plus the ability to subside the flash is the biggest advantage you cna have on a fighting rifle.
As far as the dust cloud, the hider have to be set correctly, the prone openings has to be in the 2, 4, 8 and 10 o'clock position so as it will not kick up a storm such as the guy in Vegas.