There are a few pieces of gear that I have spent way too much time thinking about. The lock is one of them. I had 4 main criteria when considering how we will keep our chariots secure:
The Ottolock is a solid balance of the first three items. Think of a steel and Kevlar reinforced zip tie that is 5 feet long and 1 inch wide (18" and 30" versions are available as well). It weighs 1/2 a pound and rolls into a coil about 3 inches in diameter. I can't truly attest to the strength of it without actually trying to cut it myself, but they have an impressive video comparing it to a cable lock.
Lighter than chains and u-locks
More secure than a cable lock
Relatively small and packable
Easy to attach to the bike
Can fit in your pocket
Can be worn as a belt!
3 digit code as opposed to 4
I went back and forth about it only having 3 digits instead of 4. Assuming 1000 possible number combinations and 2 seconds to try each one, somebody would have my bike in 33 minutes. This assumes my code was the very last one they tried. That being said, I don't have much intention of locking my bike in such a secluded place that somebody will have that much time alone to try all of the codes. At $55-$80, depending on size, it is by no means a cheap lock. It is made in America though and fills a a void in the market for being light weight, packable, and harder to break through than a cable lock. I think if you compare it to high end locks in the same price range, and consider how bulky and heavy they are, the price is fair.
We went with the 60 inch models in black. In hindsight I would order one of the bright colors next time. The black is good for Soph because everything she owns is black, white, or gray. I think it is harder for an approaching thief to see though and a brighter color might have been a better visual deterrent. All of that being said, I am glad the lock decision has been made and I am happy with our choice.