The CyBook seems to have better software/reader right now for Mobi books. The BeBook supports more formats than the CyBook. Also, the BeBook has had about 3-4 firmware updates since the last CyBook update... also the BeBook updates have added new features while the CyBook updates have been mostly bug fixes.
However, CyBook has been saying a new firmware upgrade is "immenent" which adds another DRM format (Adobe) which will expand your choices of content and will add ePub which is the "industry standard" although very new so not very popular yet, but it is growing quickly.
I haven't heard if BeBook is adding support for ePub/Aodbe.
Bottom line, either one or the other. Don't obsesse. Buy one of each, let hubby use the one you don't like as much.
BOb