Hmm, let's see. In one direction, a U-lock's entire shackle is exposed and can be cut. In another direction, using a padlock that isn't designed to hide its shackle when applied just exposes more of the shackle to attack. In another direction, that little disk lock, with its hardened steel shackle tight around the chain and chainwheel, is going to be harder to cut than anything flexible (like cables and straps). In yet another direction, obviously that little disk lock doesn't provide the resistance to attack that, say, a Xena X2 would, but it's smaller, lighter and possibly something one already has around the house.

So where were you headed with your comment?