The choice would really depend on your needs. Abus and Kryptonite are both respected brands with great products. It is up to you to make a wise choice. In the market you would be having two options, the U-lock and the chain lock. Both, Abus and Kryptonite manufacture U-locks and chain locks. Kryptonite products, especially the U-locks are very popular and trusted in the United States. Many users opine that Abus U-locks are more suited for use in Europe as Kryptonite U-locks have shackles too small, for European scene. Therefore, if you intend to use the lock in Europe, Kryptonite may not be a wise choice as you will find it difficult to lock your bicycle using it with the small shackle. However, if you are a bicyclist from New York, the Kryptonite is an amazing choice, as they have Sold Secure Gold and Silver ratings on most of their products.
The Kryptonite brand was started in 1970 which revolutionized the bicycle locking with their U-locks. These U-locks have been refined over the years to have grown in strength and have become lighter. So much so that all the other major lock manufactures, including Abus, offer U-locks now. Whereas, the Abus has been in the market since 1971. During the years in between, till today this company has manufactured every type of lock, in addition to bicycle locks. They cater to a broader market with products like chains and cables, an array of padlocks, bicycle locks, cabinet bars, electrically powered locks etc. On the other hand, Kryptonite has stuck to the narrower bicycle lock market. Recently, Kryptonite has launched many accessories for bicycles as bicycle lights, scooter and motor bike security systems etc.
Further, Kryptonite is the owner of the RealTime security GPS tracking system. With this system the owner can track his/her vehicle in real time. Kryptonite had really created the market for bicycle locks 40 years ago, and now is discovering a market for vehicle security and locking solutions.
While choosing a bicycle lock the after-sales support and the anti-theft protection schemes need to be considered. Kryptonite, as a brand is famous for their excellent after-sales support. No other lock brand has such reputation. In addition to that the Kryptonite guys throw in an optional anti-theft protection worth about $3000 when you buy a lock. Similar features are available with Abus locks too.
At the end, when you are down to buying a simple U-lock or chain-lock for your bicycle, the history and the legacy doesn’t secure the bicycle, the lock does. For the chain-locks known for their versatility, Abus and Kryptonite both are good. If you can’t decide, toss a coin. But when you are buying a U-lock, consider
(a) The price of your bicycle. If your bicycle is worth more than $400, invest in a good lock ( I recommend either of Abus and Kryptonite products with 13mm (or more) shackles
(b) Where would you be using the lock? If you are in the US, you can choose Kryptonite products for their quality and Anti-theft plans. If you are in Europe, go for Abus products.