Udi Dahan and me are currently architecting an interesting little-big project (little as it has a very limited scope for a first deliverable on a very tight schedule and big as the stakeholders require the architecture being drafted now to fit/scale for some very aspiring plans for the future - past this deliverable). It is very interesting working together seeing how different people have different styles, approaches and even directions looking at the same set of requirements and problems (and that's when we basically do have a common approach).

Yesterday Udi posted on one such difference - in the area of documenting our architectural designs. Udi thinks it is more simple and understandable to use sequence diagrams while I opted for using UML 2.0 communication diagram 

The main reason for me to choose this diagram )over sequences) was to show off my UML skills (?!) - well, not really - rather the reason was that we were trying to describe to overall context of the UI. Using a Communications diagram helps alleviate the responsibilities of the classes in the (UI) context by showing both  the relations of the main classes (actually class instances) and the main flows of messages between them. Using a single diagram allows for understanding (once you get yourself familiar with the syntax) how all the object collaborate to achieve the mutual goal of making the UI tick (I guess a better name for this diagram is collaboration diagram -but that means something else in UML 1.x).

Also as Scott Ambler mentions in The Object Primer 3rd Edition: Agile Model Driven Development with UML 2 collaboration diagrams are useful when use cases aren't the primary requirements artifact (which is the case in the particular project we're working on).

As for "visual shock" - well  I think the class diagram is less intuitive and straightforward compared with the communication diagram. what exactly is the difference between aggregation and composition and how is that different from association. Also when would you use association over dependency etc. Class diagrams seems to be "simple" because we are used them. Communication diagrams

Lastly talking about the "white-board" approach  - compared with sequence diagrams,  using communication diagrams it is much simpler to rearrange message and/or to insert a new messages in the middle of a sequence (just draw a new message and renumber the other messages)