I think people vary wildly on how they respond to the two types of leg training. For myself, I notice the biggest difference when I do heavier leg training, or at least moderately heavy. I never did squat legs from STS since I didn't have a squat rack so I did Plyo legs, which I love. I get the most bang for my buck when I do plyometrics and heavish weights with squats, lunges, leg presses etc. I do like the unweighted stuff that Cathe does too, though, like Dixie Cups (those REALLY get in there!) and many of the other unweighted moves she does in Afterburn and B&G get in there good too. I get leaner and more muscular legs and glutes doing this type of work. I could never shrink my lower body before when I only did cardio, step aerobics and pilates.
Personally, I don't get as much benefit from barre and high rep leg lift stuff. For me, I just feel like I'm doing a lot of work for nothing. I still try to throw in leg lift stuff once in awhile since I feel like I need to mix things up and shock my body, but it's not my focus.