Trunk comparison: Kia Sportage vs VW Caddy Wagon

Key Differences
With the rear seat folded down, the Kia Sportage offers a cargo space that is 20.9 in (46%) longer than the VW Caddy Wagon. When the front seats are upright, the VW Caddy Wagon has a trunk that is 6.7 in (19%) longer than the Kia. The height of the Caddy's trunk opening is 16.1 in (56%) higher.
The depth of the trunk (loading edge to trunk floor) is 0.8 in (100%) greater in the Caddy — a large percentage but small in absolute terms.
The loading edge of the Kia Sportage is 5.9 in (26%) higher above the ground than that of the Caddy. The width at the narrowest point (+3.5 in / 9%) and the opening width (+3.1 in / 8%) each differ by less than 10%, making them less relevant.
Implications for Usability
The Kia Sportage is clearly advantageous when it comes to maximum usable length with folded seats: long items (boards, slats, skis, long boxes) fit more easily when the rear seat is folded.
For everyday use with passengers in the back, the VW Caddy is more practical because it offers more usable trunk space with the front seats upright.
The Caddy is better suited for tall and bulky cargo: the significantly higher trunk opening makes loading tall items and furniture easier.
Additionally, its loading edge sits lower, making it easier to lift heavy luggage inside; the Sportage's loading edge is 5.9 in higher, which complicates loading heavy items but offers advantages in ground clearance.
The 0.8 in greater loading floor "depth" in the Caddy is hardly noticeable in practice — the high percentage value is misleading given the small absolute difference. Smaller width differences (<10%) have only marginal effects on loading bulky, wide objects; both models are similar in this regard.
Conclusion: Those who want to transport longer items and occasionally need off-road capability/ground clearance will benefit from the Sportage. Those who frequently transport with upright seating, have a lot of tall or bulky cargo, and prefer easier loading and unloading are better served by the VW Caddy Wagon.