Increasing vehicle automation presents challenges as drivers of automated vehicles become more disengaged from the primary driving task, as there will still be activities that require interfaces for vehicle-passenger interactions. Windshield displays provide large-content areas supporting drivers in non-driving related tasks. This work addresses user preferences as well as task and safety aspects for 3D augmented reality (AR) windshield displays in automated driving. Participants of a user study (N = 24) were presented with two modes of content presentation (multiple content-specific windows vs. one main window), and could freely choose their preferred positions, content types, as well as size, and transparency levels for these content windows using a simulated "ideal"windshield display in a virtual reality driving simulator. We found that using one main content window resulted in better task performance and lower take-over times, however, subjective user experience was higher for the multi-window user interface. These insights help designers of in-vehicle applications to provide a rich user experience in automated vehicles.