Trunk comparison: Audi A6 Sedan vs VW Touran

Main Differences (Summary)
The Audi A6 offers significantly more cargo length in the direction of travel: with the first row of seats upright, the trunk of the A6 is 5.5 in (14%) longer and with all seats upright even 31.9 in (238%) longer than in the VW Touran.
In contrast, the VW Touran has a significantly higher trunk opening: the opening is 14.2 in (72%) higher than the A6, and the width of the opening is also larger: by 3.9 in (11%).
Additionally, the depth of the trunk (loading edge to trunk floor) in the Audi A6 is 4.3 in (1100%) greater. Smaller differences under 10% include the loading edge height (+1.6 in/6% in favor of the A6) and the narrowest width in the trunk (+1.2 in/3% in favor of the Touran).
Impact on Usability
The greater cargo length of the Audi A6 clearly makes it better suited for long, flat items (e.g., slats, long boxes, skis with folded or upright seats) and for users who need cargo volume in the longitudinal direction.
The significantly greater depth of the A6 (more distance between loading edge and trunk floor) provides additional volume and allows better stacking of low items in the floor area; however, it can make lifting heavy loads during loading and unloading somewhat more difficult because the loading edge is higher (though only by 1.6 in).
The VW Touran, on the other hand, is more practical for bulky, tall, and wide cargo: The significantly higher and wider trunk opening makes loading large, voluminous items (furniture parts, tall boxes, strollers) easier and overall accessibility more comfortable.
Despite a somewhat shorter loading length, the Touran is advantageous due to the opening dimensions when the shape and height of the cargo are more important than length.
Conclusion: Those who primarily transport long items or a lot of volume lengthwise benefit from the Audi A6. Those who frequently load bulky, tall, or wide items and value easy accessibility are better served by the VW Touran.