It partially depended on the VIN number for me. When I was looking to upgrade there were several P85D, but many were earlier late 2014 early 2015.I just went through similar dilemma
It was between 90d and P85d, both Inventory cars identical options
90d was 8k cheaper and 3 month newer with 1500 miles on odo
P85d was 6k miles
What would be the wiser decision here?
There have been several minor improvements in the later part of the year. Some like LTE, are upgradable, but others, like the improved premium interim may not be. One minor improvement that mattered to me was the improved center armrests. The newer ones are much softer and far more confortable in my 99382 VIN, than the ones in the 60k VIN Range. It's minor, but I really like the new ones. Like the NextGen seats, they make me happy every time I get into the car.
I did drive a P85D loaner for a little over a week, and to be honest, I'm glad I got my 90D. The 90D is very close to the performance of the old P85, which is a sweat spot for me. It is very fast and fun to launch, but not uncomfortably so. Plus the 90D is cheaper to insure since its not a "performance model".