Once you reach goal, would the SB diet recommend a different maintenance plan than Atkins?

Differences wrt SBD:

much lower saturated fat
possibly higher carbohydrate levels

Otherwise, the maintenance diets are very similar, I think. However...I'm not so sure that many people on Atkins ever get to that point. Judging from my observations here, it seems as though most people on Atkins keep their carbs pretty low - permanently.

I would agree that the main difference is in saturated fat...

Atkins does say as we eat more carbs in maintenance, we should lower the fat.

Agatston spends a lot more time talking about good fats vs bad fats- and that we should avoid saturated fat. Even recommending low fat cheese and yogurt.

Another difference is that on Atkins maintenance, it is up to the individual to find their own personal carb limit (ACE).

Agatston, again, focuses more on good carbs vs bad carbs in a more general way, rather than having a personal "carb limit" as Atkins does.

But, looking at the recipes in both books (Atkins for Life, and South Beach), the main difference appears to be saturated fat. All the cheese Agatston recommends is reduced fat.

A lot of the recipies in "Atkins for Life" are pretty high in carbs, since he is catering to a few different levels of net carbs (45, 60, 80, and 100). But I don't think he ever recommends reduced fat cheese.