You could go to:Where are you quoting the Leaf and MG5 luggage capacity? I've got the MG5 pinned at 150l more than the Leaf.
Also worth noting the difference in rapid charging if that bothers you. MG5 is 70kW on CCS, Leaf+ is upto 100kW on Chademo, if you can find one over 50kW.
Personally, I'm leaning on the MG5.
464l: MG MG5 EV
420l: Nissan Leaf e+
Note that the Leaf figure of 420l is with the Bose subwoofer fitted (Tekna trim). Without, it rises to 435l.
I think the confusion comes from MG quoting two figures: one with parcel shelf & one without. Boot size measurements are odd, and manufacturers seem to measure in different ways. I don't entirely trust them. If this is the deal breaker, have a good look at the boot when you view the car & take measurements, as sometimes perceptions are misleading.