Both are great products but their ideal purpose is slightly different between them and I would personally recommend getting both. However, if you are set on just one for right now then I would suggest getting the Bug Burger. It is more of a daily diet for your feeders and is giving your chameleons the nutrition that they need.
The Superload is really a pure Gutload. Most call the Bug Burger a gutload as it does act as one but the Superload is really a pure gutload and not a daily diet for your feeders. What this means is once you receive your feeders, they don't have much if any nutritional value in them and you need to gutload them in order to pass those nutritional benefits onto your chameleon. The Superload does just that and will pack a ton of nutrients into them in a short time but after this first 24-48 hours the feeders need an actual diet that will support them too so this is where the Bug Burger comes into play.
So overall, the Bug Burger will work great all the time for your feeders and chameleons where Superload is ideally for the first initial/weekly gutloading of your feeders.