Doug B,
The sizer going farther down the case wall really doesn't have much to do with neck tension, but does affect how the rounds chamber. I'm using mine mostly for Cowboy Action Shooting, so they have to chamber through the rifles really fast and smoothly. It just works out that the old Lyman I use is also the die that sizes the brass down the most, and allows all bullets, jacketed and lead, to be held in place firmly. The fact that it has less flare at the die opening is an added bonus.
My .38 shooting isn't limited to SASS, but that's where any problems would show up in the loads. When you put 10 rounds in a tubular magazine, there is tremendous pressure on the bullets, and any that aren't held tightly in place will collapse, and tie up the rifle, which blows the stage.
Hope this helps.
Fred