what bag do you have? when I was looking to purchase something I checked out pacsafe and they had cable to attach to a secure post. the ones I was looking at did not have the lock attached to the product which is one of the reasons I went with kyss. I liked the fact the chain and lock all stored so neatly and you didn't have to dig to find the lock.
the way I looked at it is similar to they way you looked at it but my thought process was different. to me, a thief sees something chained and he walks away because it would take time and effort to brake the chain where as he could walk on a few feet and find a camera/wallet/purse just sitting on a chair. why would he waste time and possibly being seen when he could just pick something else up with no effort. I would pick the bag that doesn't show a chain because, to me, it looks easier.
if a thief wants your stuff badly enough he is going to get it, chain, no chain, visable or not. any bag that locks is just a deterent.