First off, SP II is different enough to definitely make it worth buying, especially if you are trying to follow her program. She helps you figure out which metabolic type you are:
-healthy Adrenals, insulin-sensitive (this is the goal type)
-healthy adrenals, insulin-resistant
-burnt out adrenals, insulin-sensitive
-burnt out adrenals, insulin resistant.
And like I posted earlier, depending on which type you are your P/C numbers can vary widely. Nothing in the second directly contradicts the first, tho like I said she does raise the minimum carb number. The second just gets a lot more specific.
BodyRX is an exercise/eating program. I highly recommend it, but it is a longterm commitment; a minimum of 18 weeks. It is made up of 6 week "cycles" of lifting. A 4 day split is always involved, but sets and reps change. Unprocessed, high protein food is stressed.
But if you are happy with SP, I'd stick with it.
Laura