Sorry for derailing yet another thread...

Axel, the Power Magic Pro is a device that allows you to feed permanent power to the camera (you need to connect it between your fuse box and the camera power cord), so it can keep recording in "Parking" mode when you are not running the engine, and it can be set to automatically turn off after a determined amount of hours or after sensing the battery voltage falling below a certain threshold - so you don't risk running the battery flat if you remain parked for days. If you don't get the Power Magic adapter, the camera will only turn on and record when your cigarette lighter feeds it juice - basically when the ignition is on in the case of the LR4. So, no parking mode recording basically.
I didn't get the Power Magic Pro since I have a dual battery setup in my car so I just hardwired both cameras (yes, I have one stuck on the rear window as well, in case someone rear ends me you know...) to the auxiliary battery instead, basically doing the same job as that adapter. But if you would like the camera to record events when you are parked, the Power Magic Pro may make sense.
Regarding 16 vs 32 GB, depends on the price difference. If it's only 20 bucks or so, go with the 32GB version (32 GB MicroSD cards can be had for about $20/25 on Amazon these days), lots more recording space.