I prefer the Original Blue Duox2 simply becuase no flashing is needed and comes with Two 512kb banks. Comes with Xecuter2 Bios on one bank (for xboxes 1.0-1.5) and M8+ on the other bank (for 1.6/1.6b xboxes). If you want to reflash it with a modified Bios of your own then simply use Evox or Slayers 2.6 to flash it. Evox/Slayers resizes your bios so need to worry about size of bios
The white Cromwell also has Two 512kb banks but I think was mostly made so more resellers can carry them since they come preflashed with 2 legal bioses : Cromwell and Flashbios. So in other words to run backups, install apps such as XBMC or hacked dashboards like Evox/Avalaunch you would need to reflash the chip. To reflash them you could make a bios disk, flash from HTTP or flash from C/Bios on your hard drive (the c:/bios option is only for Flashbios). The problem with the white edition is: 1. compatibility, the flashbios doen't always work on 1.6 xboxes- 2. size of bios, for most "noobs" they forget to use a 512kb bios and mess up the flash 3. flash disk for some people is hard to make one (not sure why).
The Duox2 Lite is a the little brother of the original Duox2, it only has 1 512kb bank (one is really all you need, but is good to have another as a backup). Comes preflashed with M8+ so it will work from the start on 1.6 xboxes but would need too be reflashed for 1.0-1.5 xboxes.