When looking to choose between all of the lower ab programs that are out there, there are a few things you need to take into consideration.
First think about your goals. Lower ab programs are all targeted towards different objectives, some are tailored to developing muscular size, others are training you to become more agile on your feet (good for individuals who play sports) while others are going to focus more in on getting a tight lean midsection.
Lower ab programs that are geared for muscular size will probably utilize a lot of weighted exercises where you will hold a weight while you are performing them. Since you are using an overloading stimulus this will cause the muscle fibres to break down and then grow back bigger, hence giving your waist a thicker appearance.
One that is focused on agility will use exercises that are more about maintaining stability. These will likely be done on an exercise ball, a wobble board, or by having a partner pass you a medicine ball using a variety of different actions (sitting up and down, passing back and forth and so on).
Lastly, an exercise plan that is mostly about trying to get leaner and toned should firstly incorporate a good diet and cardio plan as those are two key components of any program that has the goal of showing more muscle definition (as this is a factor of leanness). After that, it should concentrate on including exercises such as "The Plank", leg raises and any movements done on an exercise ball. The whole point of these exercises are to focus on pulling the stomach inward rather than pushing outward to develop small but tight muscles that give a streamlined appearance.
So if developing your middle is a goal of yours, make sure you shop around at the different plans and ensure the one you choose is right for what you are looking for specifically.