My experience with the posi-grip has been is that its longevity is drastically less than the sure-grip. The posi-grip started out great but after a couple of months stated to stretch and lose form, constantly rolling and bubbling up and then tearing. My posi-grip barely made it 3 - 4 month before it required removal. The posi-grip still left my hand black after each session up to the time it was done for.
The performance differnces between the two, for me, was quite evident. Three Rivers themselves responded to me that they too had experienced similar findings and the posi-grip would not hold form nearly as well as the sure grip.