The Kryptonite New York Noose 1275, is a great chain lock for high-risk settings. It's also considerably cheaper than u-locks of similar quality, but it's also much heavier.
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Pro A great chain lock for high-level security
The New York Noose has a Sold Secure rating of Gold. The chain links are 12mm thick, and are six sided instead of round, which makes them impossible to cut with manual bolt cutters. Given that any thieves would need to use power tools to break this chain, it will buy you plenty of time to save your bike, and it will also deter most thieves from stealing your bike.
Pro Less weight for the same length
The New York Noose gets its name from the cinch loop- you can wrap the chain around your object of choice like a noose. This allows for nearly the same usable length as a standard chain lock, but without the actual extra chain links, which means less bulk for you to carry.
Con Heavier than similar security-level locks
At 6.7 lbs it's not the easiest to carry with you on a daily basis.