Please note that the Movement X Series is not available any longer, but has been “replaced” by the very expensive AlpTracks family. [Editor: Nov 2017]
Movement, the Swiss freeride ski maker, has been a pioneer in wide and very light skis. The introduced the Movement Logic X (around 2.2kg at 88mm!) a few years ago. I do have a Logic X and I have to say it is incredibly light (especially with the ATK Race binding) and skis at least in powder quite well, at least in powder. See my feedback here.
The (unrockered) Logic X has been replaced by the rockered Response X (2.3kg at 177 cm).
The Response X has gotten pretty good reviews. Check out review at WildSnow.
Other tests: Outdoor Magazine (in German here: good in powder, edge grip not great, recommended mainly for lighter skiers) or Ski Magazin (in German): “… Er verfügt über eine neue Konstruktion – die Light Rocker Schaufel. Diese ist weich abgestimmt, sehr lang gezogen und bietet dadurch im Tiefschnee selbst bei schwierigen Bedingungen guten Auftrieb. Dank exzellentem Kantengriff lässt sich auch harter Schnee gut meistern. Ein echter Allrounder unter den Freeride-orientierten Tourenski. …”
As the weight difference between the Vertex X and the Response X is only minimal, I would clearly recommend the Response X over the Vertex X.