I'm fairly new to KM and before I read this post I'd never even heard of SCARS. I read this article and learned a few interesting things: http://www.fightingarts.com/reading/article.php?id=46
Some differences I noticed are:
-Cost for one thing! Yikes, $5000 for SCARS camp.
-Also, SCARS seems to be higly centralized- taught by only a select few in the know.
-It also seems to have a very scientific core approach with regards to pressure points, nerves and the scope of predictable (or documented) human response to the manipulation of these.
-While I noticed some simarlarities, particularly in the practice of combatives, SCARS probably bears more resemblance to the Military version of Krav than the now popularized civilian version.
here's link for a litte Krav info:http://encyclopedia.lockergnome.com/s/b/Krav_Maga
just a quick 2 cents, I'm no expert.