We use the ThinkGeo .NET tools for WPF, and I would vote for them for a simple application.
The support CAD drawings as a layer type, and you should be able to dynamically symbolize them relatively easily by changing the Default styles within the layer. We use shapefiles, but I dynamically switch styles for polyline/polygon/point features to make it seem like it is flashing as a selection symbol using the same styling methods that CAD drawings get theirs from.
As for supporting WPF controls on the map. You should be able to do that by arranging them on top of the map and making sure your
Panel.ZIndex value is set right so your controls are on top. I have listboxes, toolbars, extra windows, and other stuff on top of my WPF map.
Although I have found some of ThinkGeo's API documentation lacking and the occasional random error thrown from a wrapped DLL, they have been pretty good at supporting their product. They usually respond within a day or so from their forums, and provide simple examples to get you started. Also, it is an active product so you can constantly update your DLLs with daily builds (development and production quality), and if you have a good enough idea, they may integrate it into a future build.
I am not sure if the ESRI option is similar to ArcObjects with all the potentially confusing COM Interfaces. Usually I opt for ESRI since their stuff is pretty well tested and very reliable. Both softwares use the a lot of the same underlying, wrapped code, and they do most of the same processes. The major benefit for our company of ThinkGeo is the royalty free distribution of software we create. That is a huge savings over the licensing we would need to do with ESRI.
Our software (using ThinkGeo) is designed to work both connected and disconnected. The only difference in a connected environment is we then load in Google Maps. The shapefiles we use are local to each machine. We set symbology for our features through use of a database, but you can set up a window/process/whatever to have the user manually change it. That change can quickly be reflected by changing the default point/area/line styles and refreshing the overlay containing the layer.
I have been using their software for a while now and can probably point you in semi-right direction if you have questions. I would suggest downloading the evaluation version and trying it out.