Trunk comparison: Opel Astra Wagon vs VW Tiguan Allspace

Key Differences
With the seats open and upright, the Opel is clearly ahead: the Astra Sports Tourer offers not only significantly more usable interior height with the seats folded down, but especially a considerably longer loading length of +21.7 in (+117%) with the rear seats upright compared to the Tiguan Allspace.
The trunk opening of the Astra is also higher: +5.1 in (+18%), and the distance from the loading edge to the trunk floor is significantly greater in the Astra: +5.5 in (1300%).
On the other hand, the Tiguan Allspace has a higher loading edge: +6.3 in (+26%) above the road, which increases the physical lifting effort when loading and unloading.
Impact on Usability
Practically, this means: The Astra is better suited for everyday use with loaded passenger seats, bulky or tall items, and for easy loading: the higher opening and larger interior space behind the loading edge make it easier to store boxes, cartons, or large shopping; the lower outer loading edge of the Astra reduces the lifting height when loading.
For very long items that are transported only with folded seats, however, the Tiguan has an advantage: it offers more loading length with fully folded seats (by 4.7 in or 7%) and also a slightly wider opening (+2.8 in), which facilitates loading elongated or wider parts with the rear seat folded down.
Smaller differences such as the narrower spot in the trunk (Astra +0.8 in / 2%) or the 3.9 in (10%) longer loading floor of the Tiguan with the first row upright are less decisive in everyday use.
In summary: Opel Astra = better for tall, bulky, or frequently loaded items with occupied rear seats; VW Tiguan Allspace = slightly better for extra loading length with folded seats and a somewhat wider opening when transporting long items.