A Jury of one
I've been doing only Pilates and cardio for about six weeks and I have gotten softer in the glute-hamstring area so I am going back to strength training in addition to Pilates.
Keep in mind though that Pilates is more than the mat work you see demonstrated on most videos. There is a huge repetoire of Pilates moves done with the equipment that is quite challenging. Pilates also stretches the muscles while working them which is one of its greatest benefits IMHO.