Trunk comparison: BMW X3 vs Ford Focus Wagon

Key Differences
The most noticeable differences concern the height of the trunk opening, the depth of the trunk (loading edge → floor), and the loading edge height above the road. The trunk opening of the BMW X3 is 3.1 in (≈11%) higher than that of the Ford Focus Wagon.
The trunk depth of the Ford Focus Wagon is 0.8 in (≈100%) greater than that of the BMW X3. The loading edge of the BMW X3 is 2.8 in (≈11%) higher above the road than that of the Ford Focus Wagon.
Impact on Usability
The higher trunk opening of the BMW X3 makes it easier to load tall or bulky items because more pass-through height is available. At the same time, the higher loading edge of the BMW X3 makes lifting heavy loads into the cargo area more strenuous and increases the effort required when loading.
Overall, this means: for very tall items, the X3 has an advantage in fitting them in; for heavy and frequently loaded items, it is less practical.
The Ford Focus Wagon offers more practical loading comfort for heavy or frequently loaded items due to the greater trunk depth (loading edge → floor) and the lower loading edge: less lifting effort and a "deeper" cargo area that sits lower, which helps when stowing suitcases or crates.
Additionally, the Focus is slightly longer with seats folded down or upright (each with smaller percentage differences), which favors transporting longer items. A disadvantage is the lower opening height compared to the X3, so very tall items may be harder to fit through the hatch.
Width differences (opening width BMW +1.6 in, narrowest interior width Ford +1.2 in) are minor and have little significant impact in everyday use.
Conclusion
Those who often transport heavy or frequently loaded goods and value easy access are better served by the Ford Focus Wagon. Those who regularly need to maneuver taller, bulky items through the rear hatch benefit from the higher opening of the BMW X3 but must exert more lifting effort.