I think they offer a bit more control of the load which will make a difference when you're stomping up hills or riding over rougher terrain. Bungees, by their very nature, won't hold things that firm when put through unusual forces. There's a reason that most Carradice toting audaxers use one of the bag carriers availalble. It can feel very unpleasant having a heavy bag swinging around just attached to the saddle and seat post.
That doesn't mean you shouldn't try it, just be prepared for what might happen if you do and don't let it ruin your ride.
I think they offer a bit more control of the load which will make a difference when you're stomping up hills or riding over rougher terrain. Bungees, by their very nature, won't hold things that firm when put through unusual forces. There's a reason that most Carradice toting audaxers use one of the bag carriers availalble. It can feel very unpleasant having a heavy bag swinging around just attached to the saddle and seat post.
That doesn't mean you shouldn't try it, just be prepared for what might happen if you do and don't let it ruin your ride.