Certainly an option, however, a bit of a trade off which ever way you go. Here's my take on it:
CF-100:
Better quality front footage overall (weakness to lots of trees however!), small gap in rear footage
One-button press to lock files on both cameras
Has a proper parking mode (pre-buffered?) should you need it
Built to a very high standard, see niko's review on this forum
No screen (AV out can be used only to aim camera if you have compatible wire + monitor)
Not very discreet at the front unless you spray it/darken with marker pen, etc
Videos will be synced without any effort, however, both videos will be tied together in one .AVI file meaning they will be compatible with less software (can be split into two separate files using Gibson99's script)
2x A118C:
Better rear footage, no gaps, not sure about overlaps?
Can only lock front camera files as you won't be able to reach the rear cam!
Parking mode iffy, might miss important things in parking mode (can be overcome somewhat if you disable motion detection and hardwire them for constant power+use a battery discharge prevention kit+huge SD cards, but, how long will your car's battery power TWO cameras in constant normal recording mode? Also consider SD card lifespan (2x cards vs 1 card in CF-100) when used in this way)
Probably average build quality, I'm not sure, seems to be considered quite reliable I think
Small screen for aiming and playback
One of the most discreet form factors available
You will need to sync the videos yourself manually, unless you only want unedited footage for legal/insurance purposes