There are actually nearly 50 differences between the Z1 and the FX, most are electronic and DSP. For skydiving, you'd definitely want the BlackStretch for depth of color/deeper gamma. You can somewhat approximate this in post, but not quite.
Additionally, it can shoot 50i or 60i, which is critical for film or 24p matching. JAG, NCIS, and 24 are all using the Z1 at 50i to match HDCAM output.
A1 has some benefits over Z1 for jumping; it has CMOS vs CCD. The bene is that CMOS has no smear on highlight surfaces, where CCD always displays vertical smear. If you catch the sun, highlights from rigging, helmet, water, etc, then the A1 will not smear or flare those areas.
JimmyTavino, thanks for the kind wishes. I'm very much looking forward to more jumps, owning my own rig, and being able to expand my options as a professional shooter/editor.
I'll have more jump-related info later today about the A1, I'm loaning mine to a cameraman at the local DZ to shoot me and a few other jumps today. I'll edit and post footage once I've got it.