Originally Posted by Homercidal
A wing capper grips the neck and lifts up, squeezing the cap and the neck together. It may be that some necks are slightly thicker and the capper is gripping too tightly.
A bench capper simply pushes down on the whole bottle, distributing the pressure evenly across the neck. I think the odds of it causing a vertical crack are much less than with a wing capper.
My only cracks so far were vertical starting at the mouth of the bottle and running down an inch or so- and only when I was using the wing capper that came with my original kit. When I switched to a bench capper, no more cracks.