Well, I don't tour thru "big" cities, but I only carry a very thin, 1/8 inch combo cable lock. My thought is that a "pro" bike thief will be able to cut/unlock anything you use. I think the chases of me crossing paths with this type of thief is very, very slim. More likely, some kid(s) will see the bike and just want to be jerks and swipe it. They don't know what its worth and have no plans to sell it. The cable is there to just stop/slow them down while I run into a grocery store or have something to eat. I try to always keep the bike in my sight, but sometimes I need to shop in larger stores.

The thing is, the "pro" thief knows how to disable any lock. Just go to Youtube and search for u-lock. You'll find all manner of videos on how to use a Bic pen to open a u-lock with a circular key type lock. The pro's know how to cut/pry apart u-locks and they carry the equipment to do just that. I believe in more rural areas and small towns you are just as well served by a light weight cable lock as some heavy lock. Oh, and my other requirement is that it must be a combination lock. I just know that the chances of me losing the key after locking up my bike are far greater then thief ;-)