I did not use the Panasonic DVX100A but I'm using SONY HVR-Z1.
First of all, you should forget about SONY HDR-FX1 because it's a consumer product not professional like the Z1. So comparing Z1 and DVX100A, I think you already know that Z1 is more expensive but;
Here are the advatages of the Z1:
:arrow: NTSC/PAL switchable, so this enables you 24fps, 25fps, 30fps because it supports both 50Hz and 60Hz.
:arrow: 12x optical zoom (not the best but better than Panasonic)
:arrow: 1080 vertical resolution (horizontal lines) >> High Definiton (also has a built-in DV down-converter)
:arrow: 2 XLR mic inputs.
:arrow: CinemaTone Gamma(TM) & CineFrame(TM)
:arrow: Switchable HDV / DV / DVCAM format
:arrow: 5 Assign buttons
:arrow: 14 bit HD DXP (Sony Digital Extended Processor)
:arrow: 16:9 / 4:3 switchable aspect ratio
:arrow: 16:9 LCD display
...
I found a comparison of two camcorders, you can check it out here:
(some properties are left blank for Z1 but what you see on Panasoniz side, it's better in amount/quantity or at least included by the Z1)
http://www2.shopping.com/xSBS-Camco..._51001-at_least_3_in_~PRDLT-21850083-23213752
...But again, I did not use the DVX100A.
Hope you can get the one suits you best.