Well, the Bilstein
name is worth quite a bit, at the track, I'm told. Just like flashing the Porsche key-fob earns you whole seconds off your lap times, almost effortlessly!
(ahem) The question is one of unsprung weight -- with the insert upside-down, most of the mass becomes sprung, instead, which reduces transition uncertainty and helps keep the wheels on the road (generally considered a "happy place" for most wheels).
That's simplistic. If you wanted a real performance measurement, you'd have to take apart the insert to determine how much each part weighed. If you didn't feel like dismantling an expensive car part, you could estimate that it's maybe 65% on the one chunk, and 35% on the other. Then you could make an estimate as to the total unsprung weight for that corner, and you'd have something to relate that number to.
(sigh) I'm sure I'm only partially right, and that I've simplified out a lot of important variables. With any luck, we'll be able to draw out the gurus of the board (you guys know who you are!) for a great discussion of suspension dynamics.
Dan