From my perspective a twin burner and a Cadac have different functions.
The twin burner is good for car camping on my own although I can get by with a Pocket Rocket back packing stove as all I want to do is make porridge and boil water for coffee as I eat out in the evening. There's a pic of all three below.
The Cadac comes into its own for big family camping trips (twelve people) for cooking breakfasts, ommelites and boiling up big pots of water for washing up. It will also roast jacket potatoes. I only take the paella pan as I don't like barbecues and I haven't worked out a use for the scottel.
Cadacs were all the rage a couple of years ago and were over hyped. The build quality is not fantastic, the non-stick surface of the paella pan needs to be treated with care and the bags it comes in fall to bits but the Cadac is a useful bit of kit and worth having.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.