I already have a 10 pound fahgaddaboudit chain. In NYC, you can pretty much wrap the chain around anything, including thick 12" dia lamp posts. The short cable's for the front wheel though if the place's bad enough, I'll just take the wheel off and lock it to the back. Plus it's good to make a quick lockup while I run into a store for a drink. The larger cable's nice cause I can lock the back of my gf's bike and mine with the chain and thread the cable around both our front wheels and frames plus her seat.
Most u-lock's are too small to clear the front fender plus make the distance between the front wheel and downtube.