Top of the line is Abus. What are you locking to? Bike tethers set in the concrete that can be reached by a U-lock? Abus & kryptonite have substantial models. Both have folding bar locks for achieving the same security points. Both devices are popular enough that in high theft areas thieves frequently carry battery grinders to cut through them. Short tether fixes the device to hold still when being ground. Some thieves cut the mild steel fixture rather than the hardened steel lock.
My city provides racks to lock the front wheel, allowing the thief to carry off everything expensive in his van. I lock to electric poles, gas meters, and live electrical conduits. While square chains like the pagus from westechrigging.com are hard to cut, stainless steel cables as I use are lighter. 3/8" x 6' sling has kept my bike safe for 3 years. 1/2" stainless sling may be more appropriate for more theft prone areas. Abus granite is the premium lock for use with slings. A reviewer has noted that granite takes at least 2 shots of a gun to make the cylinder fall out. Slings are floppy up in the air and take 2 hands to hold still while the 3rd holds the grinder to cut effectively. My 3/8' sling rolls up to 14" diameter to fit in my pannier bag. chains fold up much tighter but weigh twice to 3 times as much for the same length.
For severe theft areas motorcycle shops sell special alloy chain that weighs a lot and takes a long time to cut through.
Note cables specifically sold for bicycles are garbage. I can cut the lumous or master cable with a hand diamalloy cutter. Not even a bolt cutter. the ones with built in combo lock, those can be smashed with a hammer or a rock.