Schmidt SONdelux Wide Body
This version of the SONdelux has wider flange spacing (50mm vs. 68mm) and replaces the aluminum axle of the SONdelux with a steel axle.
Wider flange spacing results in a stiffer wheel with more lateral strength. I doubt that this extra strength is necessary for durability--I've yet to hear of a SONdelux wheel failing under normal riding conditions because of a lack of lateral strength, and the 50mm flange spacing of the SONdelux is shared by many durable tandem hubs. However, if you appreciate a stiff front wheel (perhaps you're a larger rider, and/or you like to ride out of saddle quite a bit), the SONdelux wide body is a good choice.
All Schmidt hubs ship free to US addresses ($15 international shipping)