use the search option for lots of discussion and lots of good info from several people. This topic comes up about once a week.
In general,
DME: more expensive, longer shelf life, can get much lighter in color than LME, doesnt darken with age, is a stick mess when in contact wiht moisture humidity, stores easily in vacuum bags or plastic containers.
LME: less expensive (even on a dry pound basis), shorter shelf life, usualy cant maintain low levels of color, darkens as the product ages, is a pain to pour even when heated its tough to get all out of containers, i dont believe it would be easy to split up into other containers.
A gentlmen from Briess did a real good interview on brewing network one time that you can download for free.