If your banding them really young I wouldn't use the cable ties, incase one gets too tight, they can be a hassle to cut, especially if its tight around the leg. I like to wait until their older so that the leg band fits over the foot snuggly so it won't fall off. But then again I use the sealed...
Its mostly for showing and breeding purposes.. and for large flocks..
Alot of places require them.
I buy smaller sized leg bands from Strombergs for my breeding pigeons.