'Soft vinyl' is rather something of a misnomer but seems to be an industry term. People hear soft vinyl and think of squeeze toys they'd give their pets or small children. These are solid and carry some heft for their scale and construction. IMHO the material used is also ideal for capturing the sheen of actual stormtrooper armor -weathered in this case - without any glossy overtone that would detract them as big action figures. I guess 'soft' refers to the flexible properties when assembling, ie. heating the attachment points for easier fitting, or even the fact these won't shatter like resin if dropped - god forbid! I do think resin however is better in capturing human likenesses.
