X-flex and Vision have almost the same shape and weight, because the thicks 7 mm monofilm panels are heavier than the x-ply monofilm but the pvc window of the X-flex balance that difference. Obviously the X-flex is little more lasting than the Vision, especially if you broke a mast and sail get folded by the waves, but the 7 mm monofilm of the Vision are quite bulletproof as the x-ply until is used properly (rinsed and dried after the use, not let stand in the sun for long).
The real difference beetwen the two sails is about the kind of feeling that the two materials gives.
The X-flex have a smoother feeling on the wave (K. Teboul likes this kind) while the Vision is more “powered up” because its profile is more steady and with less bounce giving you more speed to execute aerial moves and snappier reactions to complete air trixs.
The amount of downhauling is quite constant, while the trimming is mostly obtained by working on the outhauling giving more or less tension in order to give more deepness (power) to the sail.