Hi Nancy,
I don't know a whole lot about Scarsdale, but in my opinion it's stricter than the post-Induction phases of Atkins. From what I know about Scarsdale, it's more planned - you eat certain things on certain days, and it's lower fat as well as low carbs. One of the things that I like about Atkins so much is that you can eat things like full fat salad dressings and cheese.
I suggest checking out lowcarbfriends.com and going to the challenges bulletin board. There's a daily Scarsdale thread that you should be able to get some information from. I read it every once in a while and people seem to lose very quickly. I've toyed with trying it but like I said I like being able to eat higher fat than Scarsdale seems to allow.
Good luck!

Jennifer