Its amazing that Teslas are still so new that we don't have a lot of history or a good model on depreciation. I can be wrong but my gut tells me the X holds its value longer than the S just because it can fulfill more functions. Even if you lose more dollars at year 3 for a 100D vs 75D, the 100D still has more utility value because you can amortize the lack of needing to stop for SCs and general comfort of less range anxiety over the life of the vehicle. It's hard to model that but you will see that when you make those ski trips.
It matters to me too but why I considered a 90D versus the 60D was the 90D has better performance. Ultimately went with 60D just because it was such a bargain and I can live with the limitations. With the 60D out of the picture, 100D is the best car for the money. I would trade any other option such as PUP to stay with that.
The neat thing about the Model X is it seats 6. That allowed me to remove both an Audi SUV and a Honda Odyssey from the car fleet. No matter what vehicles come and go later, the Model X will always be a nice people and cargo carrier. It will reach a certain point where the depreciation curve will flatten. And it will be many multiples above a leaf for two reasons:
1 - It's a Tesla SUV
2 - It's not a Leaf.
A Model 3 will be added to the family when its available and I can forsee that 3 being replaced again before the X is.
The 100D battery will be in good shape for a long time, you can charge to just 90% for the almost the whole life of the car.
AP2 hardware once fully mature from a software perspective should be "good enough" for autonomy. AP3 of course will be better but only marginally. AP2 was a huge leap over AP1 so that creates a good "break point" to buy and go long on a Model S or Model X purchase today.
I'm glad you did not mention leasing. It can work for some people in very specific situations but overall I feel the numbers are HORRIBLE.