Atkins allows less carbs than SB, and also allows for fattier meats and other foods (like butter and cream) than SB. You are also trying to get into ketosis on Atkins, which causes some yucky side effects like "dragon breath." We try to avoid that on SB.
SB focuses on good carbs, good fats, and lean proteins. It isn't about counting carbs like Atkins. I would highly recommend getting a copy of the SB book and reading it for a good foundation before you embark on this, and we can also answer questions here when things get confusing.
Yes, lentils and beans/legumes are allowed starting in p1. You can see the full p1 food list in the FAQ on this board.
-- food lists, portion guidelines, etc.
SB since Nov '03
Goal: major weight loss (50+ lbs) & good health
Reached Jan '05!