It depends on the circuit and what you what the workout to be. If it's a workout that's more like a 'cardio with someweights, but keeping cardio intensity," then I'd go lighter on weights and focus on the cardio. If it's a "weight workout with cardio intervals to keep the intensity up," then I'd go heavy on weights. If it's something in between, then you can focus on one or the other, depending on your goals or mood.