The ID.3 and the EV6 don't really cross shop, if you are looking at the EV6, you should be comparing it to the ID.4. The ID.3 is Golf/Focus sized hatch, the EV6 and ID.4 are much larger, like a Tiguan or Q4.
Yea, I didn't really make this clear initially - I'd initially thought I'd go iD.3 first, however having looked at the size (like you say, Golf/Focus size, and I have a focus now) I think the step to EV6/iD.4 would work for me, especially as I expect there may be a couple of tiny feet in the family by the time I buy