When I was going through the same dilemma, this thread,
What to Order -- X 75d, X 90d, X 100d was really helpful. Most of the folks favored the 100 as I suspect this thread will reflect as well. We did eventually pick the 100D but even after picking it up, I'm not convinced it was the right choice. For one, it feels heavier than the 75D we test drove. Maybe it is just my imagination or maybe a new car needs time to break in - although it's not like an ICE where there's are cylinders and transmissions to wear in. I supposed the gear box to a much smaller extent.
I think the main consideration, at least to me, should be whether or not you favor road trip vacations vs. flying to your destination. For everyday around time use of the car, a 75D is ideal. You save $18K (tax included) and it is a bit more efficient due to less weight. One road trips, it's not that you can't get most places with a 75D but that you would use the limits of the lithium ion battery pack which causes some degradation. There's also the consideration of faster supercharging and even skipping a few during the long distance route but those factors are less important to me. My family enjoy frequent stops.
So why did I go with the 100D? My frustration has been the lack of official communication from Tesla about whether or not you can upgrade to a 100 kWH battery pack later. There's lots of threads debating whether there are suspension differences that would make the upgrade unpractical. If an upgrade is made available later, I would argue it is better to get the 75 kWH pack now and replace it with the 100 later as it is almost a guarantee the $/kWH will drop in the not too distant future. I think about it the same way I think about computer hardware. I always buy the second best graphics card for my PC. It is much cheaper, almost as good and next year I'll be able to buy last year's top of the line GPU at a fraction of the price.
You'll find most here will say buy the most you can afford. But I tend to look at it from a value perspective. Breaking out the math on a spreadsheet, the value is definitely with the 75D. You get 100% of the features (sans the 72 amp AC charger) for $18K less. My wife drives the 100D and she drives less than 30 miles a day. I have the car set to charge to 70% to favor 50%-70% SOC. 72 amp charger would be overkill for replenishing 30 miles of range. That would take an hour at L2 40 amps. This will be the situation for 95% of the time we own this car
Will the 100D come in handy for the other 5% when we're road-tripping? Absolutely. But you have to decide whether you want to pay $18K to optimize for that 5%. That's my situation and my 2 cents. Yours may vary.
[Edit] Oh I forgot the 0-60 of 4.8 seconds bragging rights if that matters to you. Obviously not a big deal to me since I didn't include the difference in my original post