I would get the largest diameter cable that I could find, or one of the new armored cable locks.
Weight for me isn't an issue. I have a U-lock, a cable w/padlock, and a chain w/another padlock. I want to get a ring or frame lock too.
Having said that, I rarely lock my bike up, in my area, it isn't that big a concern. When I go to the city, I use all the locks and remove anything that is semi-removable (lights, bags, etc.)