On monetary terms the ID.3 Max power is the one to go for, the ID4 equivalent is far too expensive unless there is a bib price cut in the AP on 1st Oct.
For us the ID3 tour/ID4 pure was an easier but still difficult choice as it’s £1349 v £2900 and possibly less if the AP comes down.
The major difference in our case is the range between the two as the 3 has a 77kw battery where the 4 has a 52kw.
We test drove both last week and liked the 3 a lot as it was nippy and a more involving drive especially on smaller twisty roads. Where the 4 scored over the 3 for us was space, bigger boot, easier access, more comfortable seats and rode better over bumpier surfaces. So depending on what you want that is your choice, we are ordering a 4 later today and if the AP comes down the dealer said he would re order at the lower price. If the 4 with larger battery came down a lot we might even go for that one.
Hope that helps you.