Trunk comparison: BMW iX1 vs Peugeot 208

Main Differences
The BMW iX1 offers a significantly longer cargo area with the rear seats folded down: +12.2 in (24%) compared to the Peugeot 208. Even with the front seats upright, the iX1 has noticeably more trunk length: +9.1 in (34%).
The trunk opening of the iX1 is also wider: +9.1 in (27%) compared to the Peugeot 208. In contrast, the Peugeot 208 has a significantly greater depth measured from the loading edge to the trunk floor: +6.3 in (800%) compared to the iX1.
Implications for Usability
The longer cargo areas of the BMW iX1 (with seats folded and with front seats upright) make it better suited for long items like boards, skis, or longer luggage as well as for larger, flat-spread loads.
The wider trunk opening of the iX1 makes loading and unloading wide items (strollers, boxes, furniture parts) much easier.
The greater depth of the Peugeot 208 (more space between the loading edge and trunk floor) creates more room below the loading edge, which helps when transporting taller or unevenly stacked items and allows small items to easily "disappear." At the same time, this deep recess can mean that heavy items need to be lifted a bit higher to get over the loading edge; however, the slightly lower loading edge of the Peugeot (only 0.4 in difference) mitigates this.
Smaller differences—such as a 1.2 in higher opening on the Peugeot or a 1.6 in wider interior width at the narrowest point on the iX1—have only minor practical effects.
Overall: those who frequently transport long or wide loads benefit more from the BMW iX1; those who benefit from a deeper cargo well and somewhat easier access for smaller loads find advantages in the Peugeot 208.