I have a VPfree and a Heckler and would rather climb on the Free. The VP linkage is great, especially climbing smooth stuff. When things get hairy in the small ring there is a fair amount of feedback as the chain fights rear compression but by contrast the Heckler likes to sink in its travel and stay there. The Free is a much more solid feeling ascender.
Some platform does seem to help the Heckler but is a detriment to the Free. Contrary to some opinion, single pivot + platform is NOT the same thing as a virtual pivot. A platform valve is basically on/off. Once you've broken it, the assistance is gone. With VPP, the degree of "platform" you get is directly related to how hard you are pedaling, instantaneously. Light on the pedals, light assistance. Downhill - no assistance, pure squish.