HDD and flash memory compression (AVCHD for hidef; MPEG 2 for standard def) should be the same. Which is lots.

You are missing one other item - manual audio control. Personally, I'd recommend the Canon HV30 or Sony HDR-HC9 for a consumer camcorder - they are miniDV tape based and require you computer to have a firewire 400 port port for DV and HDV import. DV and HDV format digital video are the least compression of the currently available consumer storage media - and as has been posted here previously, I won't repeat the myriad other advantages of miniDV tape vs other storage media.