Trunk comparison: Hyundai Elantra GT Wagon vs Tesla Model 3

Summary of the most important differences
Looking at the cargo concepts, two differences stand out clearly: The height of the trunk opening is +5.9 in (≈29%) higher in the Hyundai i30 Wagon than in the Tesla Model 3, and the depth of the trunk (distance from loading edge to trunk floor) is +4.3 in (≈1000%) greater in the Tesla.
All other measured deviations (cargo length with folded seats +5% in favor of Tesla, cargo length with upright first row +2% in favor of Tesla, loading edge height +8% in favor of Tesla, narrowest width +7% in favor of i30, width of the opening +2% in favor of Tesla) are significantly smaller and more moderate to assess.
Impact on usability
The significantly higher trunk opening of the Hyundai i30 Wagon makes loading and unloading tall or bulky items easier: large boxes, plants, skis, or furniture parts can be loaded standing up or with more clearance because the vertical passage is higher.
This reduces the risk of bumping against the opening and facilitates handling when loading without assistance.
The considerably greater depth of the Tesla Model 3 (distance from the loading edge to the floor) practically means more "recessed" space behind the loading edge. This is advantageous for flat or long items that can lie deep, as well as for using lower, well-stacked loads without them protruding over the loading edge.
However, this recess can make lifting heavy items out of the interior more difficult, especially since the Tesla's loading edge is somewhat higher above the road; heavy lifting requires more effort because items must be lifted from a deeper position.
In practice, this means: Those who frequently transport tall, bulky items (e.g., plants, tall boxes, furniture pieces) have easier loading with the i30 Wagon thanks to the higher opening.
Those who often transport longer or flatter loads and value a deeper cargo space behind the loading edge (e.g., long boxes, numerous flat pieces of luggage) find advantages in the Tesla Model 3. Smaller differences in length and width only slightly affect everyday usability: the Tesla offers somewhat more length with folded seats, the i30 slightly more narrow width at the narrowest point.