Well, reviews are subjective, so nothing extraordinarily odd there.
But when it comes to a racquet or string's arm-friendliness, I trust my arm the best.
You should always demo for yourself before buying a frame, but if you're going to listen to anyone, you can choose to hear from a guy who has an ultra-sensitive arm (yours truly) because of his previous bouts with tennis elbow, or from someone else who might have a perfectly healthy arm and cannot tell apart the harmful shock that jolts the arm from a harmless ping from the stringbed.
Plus, the other posters who compared the X-Fast Pro to Pure Drives in that thread did not specify which version of the Pure Drives. My comparison is to the 2012 models of Pure Drive Plus and Pure Drive Plus Roddick. From what I hear, the 2012 versions are far more comfortable than their predecessors.