Trunk comparison: Citroen C3 vs Ford Focus

Key Differences
The Ford Focus offers significantly more cargo length: +7.5 in (14%) when all seats are folded down and +3.9 in (15%) with the front row upright compared to the Citroën C3. The width of the trunk opening is +4.7 in (14%) larger on the Focus.
In contrast, the Citroën C3 has a +2 in (28%) greater trunk depth (distance from loading edge to trunk floor), and the C3's loading edge is +3.5 in (13%) higher above the road. Smaller differences (e.g., trunk opening height +0.4 in and narrowest width +2 in) are rather insignificant.
Impact on Usability
For long items (e.g., slats, furniture panels, folded skis), the Focus is more advantageous: the longer cargo areas (both with folded seats and in normal condition) allow storing longer parts without complicated positioning or partially placing them in the footwell.
The wider opening of the Focus makes loading and unloading wider items easier and reduces the risk of corners hitting.
The Citroën C3 offers more usable vertical height in the trunk bed due to the greater depth between the loading edge and floor, which helps when stacking taller items inside the cargo space. Practically, this means: for bulky but not too long loads (e.g., stacked boxes), the C3 can provide more capacity vertically.
At the same time, the higher loading edge of the C3 makes lifting heavy items into the trunk more difficult; loading and unloading require more effort than with the lower loading edge of the Focus.
In summary: Those who frequently transport long or wide cargo benefit from the Focus. Those who need more usable depth for stackable, bulky cargo and can manage a higher lifting effort have advantages with the C3. Smaller differences in opening and interior width are usually negligible in practice.