The food is amazing and the price is actually lower than many of the other meal programs I've looked at. They also offer superb customer service which is crucial to me.
From my understanding, the calorie differences are due to portion size. They make the diet in larger portions for people who need more calories (the same food only more of it). I am not positive of this, but one of the reps made it sound like this was the difference when I also asked about this some time back. They are very helpful so perhaps you should just give them a call and ask. It's 1-800-743-SLIM and just push 2 when you get in and that will take you directly to customer service.
I should be getting my food tomorrow for the low fat plan (I have been on the low carb for a month and lost 10 pounds). Excellent food by the way. This should really all go in the Diet To Go thread we already have in place (not sure if they can merge it or not, but thought I would answer you here because you may not realize this). They do not include snacks which doesn't bother me because most of the meal delivery plan snacks are all chip and soy products which I can't have due to my thyroid problems. I prefer adding my own and save money as well. I usually have either a cup of hot cocoa or a low carb chocolate bar at night and eat an apple or a piece of string cheese in between (I also have a glass of milk per day) and am losing just fine.
Hope that helps. Good luck to you.