A little summary:

P400 has definitely better dynamic for sure but in the long run it will have issues (subjectively collected from forum statistic):
there's no perfect MHEV system, that alternator/generator will fail and might get you stranded in worst case scenario.
more coolant leaks than P300
Water leaks have potential to destroy more stuff in cargo department (MHEV components)
It looks like mostly P400 have that steering locking issue
weight distribution
P300 final drive ratio and 18" wheel option
________
P300 does seem to run hotter, brakes are mushier too.
________
Both engines have timing chain components unserviceable, have to pull whole thing out.

 

Thank you everyone for the good advice and sharing your experience. Now, a set of (stupid) follow up questions ....
I get that the P300 is not MHEV ( not that I miss that ) ?
On the ordering part, and I know, there is an entire thread out there, but if I spec it to my liking, I there the risk (still ?) to get whatever the manufacturer feels like that week ? Most interested in HUD and the mirror ( however I am now testing one on a Toyota, a cheap Amazon one, and it is eons better than JLR OEM one ). Still it would be nice to have the OEM.
Yes, the 18" wheels are something that I like a lot.
I have been trying to find a P300 X-Dynamic at a dealership already, and could not find one in the continental US that has the features above described. Oh, and one very last question: when I got my D 110, I could order it without sun roof. I don't care much for it. Can I still order a Defender without a sun roof ?
Thank you all again.

 

For the NAS market the sunroof is in the price, you can ask to delete or pay $ 400,- for the folding roof to get rid of the glass.
No x-dynamic for the P300 currently offered, but I have to say the P300s is fairly good in it's specs.
( standard with heated seats- and steeringwheel, privacy glass, ACC, Meridian, Premium headlights & fogs, sunroof.
In Europe these are all options)
Too bad it can't be ordered with Ebony headliner and Dark Grey crossbeam.

Did a config, for $ 65.000,- you get a great D90 - so enough room left for retrofits to give it a x-dynamic look

https://build.landrover/1DBB24C6

 

Thanks for the build, that looks pretty much what I need. However, I still need to think about the roof. The thing is, I just need a plain vanilla roof, with no gimmicks ...I never use it and it is another thing that can go bad.