Lorrie, I think you got a good range for strength training.
For me, PS burns the most calories of all the different workout series. As well as it seems to be a bit different then the others as well. All of the strength workouts have their own challenges, but the main thing is with PS, I get stronger rather then bulk, something I can say about the others. But everyone is going to have a difference experince with the the videos, some may not show much gain, other will show quite a bit in only small time frame. So it's really up to you, though if you like Cathe you'll probably end up getting it sooner or later anyway.
Kit