The CX-9 and Sorento have about the same amount of cargo volume on paper. 71 vs 73 cu ft overall, 38.2 vs 38.8 behind the 2nd row, and 14.4 vs 11.3 behind the 3rd row.
For comparison the 2018 Traverse, which they say is fully class competitive again, has a third more volume overall, 50% more...