I have to agree that using boot capacity as a comparison between cars is hugely misleading (even though I have done it myself). We have recently moved from a VW Tiguan to a BMW X1. Looking at the official stats, the Tiguan boot is far bigger but, in reality, the X1 boot is far more practical and feels a lot bigger when it comes to usable space.
My wife has a wheelchair which I remove the footrests and seat cushion from and then fold in half and lift into the boot. In the Tiguan it was a real squeeze and would often stop the auto tailgate from closing. In the end I had to roll the rear seat bench forward slightly and put the back rests slightly more upright to avoid this. In the X1 we don’t have sliding rear seats so they are fixed. The backrest angles are adjustable but I have them in the most reclined position. In spite of this, the wheelchair goes in with room to spare. In addition, under the boot floor in the X1 there is an absolutely huge compartment that is almost like a second boot. I don’t think that this is calculated in the load area as it is below the load floor. It is about a foot deep and runs the whole width of the boot and at least two thirds of the length. I have loads of stuff in there, leaving the main boot clear for the wheelchair. In the Tiguan there was no usable space at all under the boot floor.
The Tiguan is a couple of inches taller than the Tiguan, so the extra capacity on paper is probably due to that and that’s space we never use. So on paper we have a smaller boot but in reality it feels a lot bigger and is far more user friendly. As others have said, the key is to check the dimensions and get a decent test drive to see how what you need to carry around fits.