There’s afew advantages but it’s not pixie dust and they are only as good as the work you put in to them.
As Gavin said above, you are going to the river not only with something as fresh as it possibly can be but also unique and probably something the fish haven’t seen or tasted before. Do something different with the shapes too and you’ll have a complete 1 off bait with your own label on it.
Now the real advantage comes with application and I’ve witnessed first hand how devastating this can be with HNV baits.
To get the best out of them You need to be introducing it with very low levels of flavour at least 2-3 times a week for 5-6 weeks in 3-4 swims before you put a hook bait out and after that period you continue applying the bait while fishing them.
Doing this you are no longer attracting your barbel by smell but by taste. They will be actively looking for your bait and recognize it as a food source but it’s important you get the recipe nailed on because if the taste ain’t right, it doesn’t work. Hence very low flavours.
This is a really powerful thing in tricky venues because you have added your high nutritional value bait that tastes great to the menu of foods that they will be looking for as part of their diet. You can’t do this to the same effect with over flavoured low nutrient shelf life baits.