Size: Hmmm. difficult to say, bootlength is fractionally longer, The rollator fits in with room to spare, on the X1 it was exact. The tailgate is more sloped so less space at the top but roofline seems a bit higher. No underfloor space in the boot. Seats fold down to give similar space I think.
The car is a little wider and the cabin feels more spacious. Better storage compartments. Instruments and controls (especially heater) are better than the 2017 X1.