Circuit training is proven to be better for fat loss. Cardio is great for your heart but you will not build muscle doing it. Your metabolism will run higher with more muscle mass.
Circuit training comes in many shapes & forms. As you mentioned doing straight cardio & then pure weights is one form. Another form is doing 1 set of reps for one body part & moving to another body part in a circuit with no rest between exercises--for example, doing 1 set of 12 chest presses, 1 set of barbell rows, 1 set of squats, 1 set of barbell curls & 1 set of tricep dips & then doing that whole circuit again.
Try a couple of Cathe's circuit style workouts; Circuit Max, Body Max, Boot Camp & Cardio & Weights, for effective total body workouts with cardio. Cathe is also in production with a new series that will include a circuit workout as I described above.
Hope that helps.