I did a test with both balls (distance only) off the tee in low winds. After each drive i recorded the wind direction and distance and only counted the shots that dinged or almost dinged. I also aimed at the same place on the fairway. After 150 drives on 3 different course's (75 of each) the results showed there was no real difference ...if anything the normal z balls went a touch longer.
After the test i went back to the normal Z's, not only cos of my findings, but i feel there's no need for any extra spin....if you really do get extra spin..lol