The big difference is that the post-surgical program is designed to start the day after surgery to encourage mobility, diminish pain, and build strength so your pet gets up and moving as soon as possible to maximize its chances of a full recovery. 
Now, if your pet hasn’t had surgery, I recommend the nonsurgical cranial cruciate ligament program, because this is designed for pets recovering from a partial or full CCL tear but that have not had surgery. 
If your pet has had surgery weeks or months ago to repair its CCL, I don’t recommend starting the post-surgical program, because, as I said, this is designed to start day one after surgery. I’d recommend starting the nonsurgical medical-management program in that case.