Also, what's the difference between Insane/Ludicrous/Ludicrous+? Do people keep it in Ludicrous mode the entire time, or does that drain the battery faster? Is Ludicrous + only for special circumstances?
So I feel well qualified to answer this because I drove an X75D for about 18 months, then just got my X P100DL a few weeks ago. I also have a Model 3 Performance for reference.
So the X75D is fast, but it's not make-your-stomach-drop-and-head-cloud fast. It's weird but once you get to a certain acceleration, it's not just fast but almost uncomfortably fast. Like if you had a big meal you wouldn't want to do that because you might lurch. NOT that this is a bad thing, it's just an intense acceleration. It's one that can catch your passengers off guard and some passengers go fight-or-flight if they you gun it and they aren't expecting it. I never had that in my X75D. The Model 3 Performance is that fast as well, but the XP100DL is just a touch faster.
So with your model X75D, you have Chill and Sport mode as your two acceleration profiles. An X Performance (formerly P100D) without ludicrous will also have Insane and Insane+ mode which are a good step up from the Sport mode you are used to on the Model X. It's what I'd think most people would expect when I say "Very fast sports car". Ludicrous and Ludicrous+ mode replace Insane and Insane+ and are just another level above that. I remember my first time on a super sports bike (Yamaha R1) and my response to that acceleration was "I just didn't know they could make vehicles accelerate that fast" and I think Ludicrous and Ludicrous+ are like that for a lot of people. It's not quite as fast as an R1, but in any case I think lots of people who experience it don't realize that something, much less an SUV, can physically accelerate with that much vigor.
As far as what driving mode you want to keep it in. Sport mode is going to be very similar to the sport mode in your Model X 75D. Ludicrous mode is going to be very similar as well, and if you're driving nicely you won't even be able to tell the difference. The pedal response for maybe 2/3 of the travel is (nearly) identical insomuch that I don't notice if my mode is changed most drives.It's that last 1/3 of the pedal travel that ramps up, way way way up. It's like imagine this whole time there was a little wooden block under your Model X 75D pedal so you could only push it part way down, now you can put it in Ludicrous and push it all the way down and get the full power. You can still drive the same as you always have, it's just that last end of the pedal travel that shoots up. (Note: The physical travel of the pedal doesn't change, just the power curve).
Finally + modes are just for showing off. There's a number of little tweaks it does, like heating the battery, to eek out that last little bit of power to make it as absolutely fast as possible. It drains a ton of battery to heat the battery and the difference is really not that big. You wouldn't ever put it in + mode during daily driving, only if you were going to drag race or to show off or whatever.
