the reason they revised the shape was to get the short cases, like 9mm, to feed into the tube ...in the old style shape - they had a tendancy to roll sideways as they dropped out of the feeder plate and into the funnel
They revised it because there was a white insert called the "adapter funnel" (part # 13688 page 8 in the casefeed manual) that you had to install for 38 super and smaller cases. The new design eliminates the extra part and the time it takes to install/uninstall it. Win, win. Works fine and won't stack cases if you follow the instructions.