Trunk comparison: BMW 5 Series Touring vs VW Tiguan Allspace

Key Differences
With the seats folded down, the loading lengths of both models are the same. However, with the rear seat upright, there is a clear difference in favor of the BMW: the BMW 5 Series Touring offers a cargo area that is 24.4 in (132%) longer with the rear seat upright.
Additionally, the loading edge height differs noticeably: the loading edge of the VW Tiguan Allspace is 4.3 in (17%) higher above the road than that of the BMW.
All other differences (e.g., +1.2 in length with the front seats upright, +0.8 in opening height, +2.8 in narrowest width on the BMW, +3.1 in opening width on the Tiguan) are each under 10% and thus comparatively minor.
Impact on Usability
The significantly larger cargo area of the BMW with the rear seat upright makes it more practical for everyday use: groceries, suitcases, strollers, or bulky items can be stored more easily and usually without folding down the seats in the BMW.
Those who often drive with a full load of passengers and regularly need storage space will benefit from the BMW.
The higher loading edge of the Tiguan makes lifting heavy or bulky loads into the vehicle more difficult; this is a noticeable disadvantage when frequently loading heavy items.
The slightly larger opening width and the slightly higher opening on the Tiguan marginally improve loading bulky parts, but these advantages are small (<10%) and do not compensate for the higher loading edge.
Conclusion
For users who need a lot of usable cargo space with the rear seat upright, the BMW 5 Series Touring is the better choice.
The VW Tiguan Allspace offers only slight advantages in opening width but is at a disadvantage when handling heavy loads due to the higher loading edge. With the seats folded down, both models are equivalent in terms of loading length.