Couple suggestions I would make would be:
1. Use somethung like Apple's Time Machine (or a similar Windows product) vs a mirrored raid. Mirrored drives always made me nervous. Yeah, you get 2 copies of everything but you also copy any mistakes automatically. You know, those "..aw #$%^, noooo.. " feeling you get as you start to lift your finger from the 'return' key and the drive lights start blinking.. ;>
In TM drive 1 is the primary that the laptops sync to. That drive (actually changes to it) are then backed up every hr (or on command) to the 2nd drive (usually 2x the capacity of the first). However, the older data from last run is not deleted - if interested, read Up on Time Machin and, if on Windows machines, what similar products might be out there to do incremental backups with caching of older items.
TM/Windows equivalent allow you to 'go back in time' x hrs or days and retrieve files added in the last backup should you inadvertendly delete a file(s) using either laptop. Very efficient and works as advertised.
2. Keep the disks physically seperated. Avoids one coffee or errant elbow from taking out both and if one power supply goes, etc, only one drive is taken out. At worst you lose 1 hr's work or less.
3. Clone the 'Time Machine' target drive on a regular basis.
If using TM, the disks aren't bootable, so backup your applications, etc using another drive. I personally love using 7200 rpm drives in drive docking stations, along the lines of the ones mentioned above, or the units sold by OWC (below).
http://eshop.macsales.com/shop/NewerTech/Voyager/Hard_Drive_DockI no longer buy discrete drives (e.g. ones with one power supply). With a dock you can use your drives of choice, vary them (e.g. WD in one, Hitachi in another, 3.5 or 2.5, etc.). If a drive(s) are only used occasionally, it keeps the myriad of power cords and bricks down as you just pop it into a dock when you need it, backuo, pop out back into storage and put other drive back in.
I use the multi-interface units so can use with USB, FW or PCI Express as desired (or if helping a friend out).
Can't really comment on syncing between laptops.