Trunk comparison: Audi Q5 vs BMW 5 Series Touring

Main Differences (only values >10% highlighted)
The BMW 5 Series Touring offers significantly more loading length: with the seats folded down, the trunk is +9.4 in (14%) longer, and with the first row of seats upright, it is +5.5 in (15%) longer than in the Audi Q5. In contrast, the Audi Q5 has several advantages in the vertical area: the height of the trunk opening is +3.5 in (13%) larger, the depth between the loading edge and the trunk floor is +3.1 in (700%) greater, and the loading edge is +3.1 in (12%) higher above the road than in the BMW 5 Series Touring.
Impact on Everyday Usability
More length in the BMW 5 Series Touring means better usability for long items (e.g., skis, long boxes, planks, or folded bicycles): with the seats folded down, longer, flat-lying loads can be accommodated more easily. If long cargo is regularly transported, the BMW is clearly advantageous.
The advantages of the Audi Q5 lie in vertical packing capacity and interior profile: the higher trunk opening facilitates loading tall items through the opening itself, and the significantly greater depth between the loading edge and floor creates a deeper cargo compartment where items can lie further "down" — practical for stackable or bulky but not too tall cargo.
However, the loading edge of the Audi is noticeably higher, which makes lifting heavy loads into the trunk more difficult; those who often lift heavy items will benefit from the lower loading edge of the BMW.
Small width differences (width at the narrowest point +1.6 in in the BMW; width of the opening +2.8 in in the Audi) are under 10% and have little practical impact.
Summary
For long, flat cargo: BMW 5 Series Touring. For more vertical packing depth and larger opening (with an acceptable higher loading edge): Audi Q5. Those who often load heavy items will find the lower loading edge of the BMW advantageous.