Move Silently vs Hide in Shadows (Is there any difference?)

I'd like to settle this once and for all, does move silently do anything that hide in shadows does not? All I see is speculation, "I think move silently also determines stealth when you move", "I think move silently determines how long before you leave the shadows after attacking", etc.

The only concrete evidence I've seen on the topic is this extremely insightful post:
http://social.bioware.com/qnwn.net/forums/forum/1/topic/183/index/12667733/1#12882261