I believe that tesla has made some updates over the years and I would only be interested in a car that has the most updated computers, etc. I would like the ability to go to FSD at some point.
There are obviously a ton of small changes that are very difficult to track. But some of the more significant ones:
Rear motor - outlined above.
HW3 computer - timeline covered above. Build date later in 2019 should ensure that's what you have, and I think there's some easy way to ID it (I think there might be a way to look under the glovebox or something but I don't remember). (Ah - "FSD Computer" I guess is visible on the screen it sounds like?)
Heat pump: Late 2020 builds (must be 2021 model year) include this as mentioned above. Can help achievable range in cold winter climates substantially. (Is the main reason for the 322 -> 353 rated mile bump since it changes the scalar used; does not substantially change efficiency in best-case conditions (no heating/cooling) though.)
Note that the range bump from 310->322rmi (actually possibly 332rmi if you read between the lines a bit, since the 2020 Performance 18" measured at 332 rated miles and was reduced voluntarily to 322rmi) may well apply to almost all 2018/2019 vehicles (there were multiple software improvement to increase efficiency, but they are not reflected in the displayed rated range for older vehicles, but that doesn't mean the range isn't improved). So end result is you're looking at something like a 7% increase in range in 2021 (~332->353), subject to the caveat that that would happen only in somewhat chilly conditions, where the heat pump was helping you that much, and the improvement would be less at high speeds, where range really matters, because there aero losses are a larger percentage of the overall force required to move the vehicle, and Wh/mi allocated to heating is reduced the higher the speed (shorter time to travel each mile)). This is all with an identical battery size; no assumptions about increased battery size.
Larger battery: Transition to 82.1kWh occurred sometime around Q2 2021 in AWDs. All 2021 Performance, regardless of build date, seem to have the 82.1kWh battery. All earlier LR/P vehicles (2017, 2018, 2019, 2020) (except perhaps the very first RWD, but these are very rare, so I have no idea) started with ~77.8kWh batteries.
(This whole 2021 battery discussion is for the
US vehicles only - it's MUCH more complicated for European vehicles since they have all kinds of batteries used.)
One important thing to watch for, for a well-used car is to look up the post on how to assess battery health in the Battery section. You can use the energy screen to get within ~1kWh of the value (assuming degradation has started to show). Generally the BMS estimates are pretty close (there are rare exceptions), but you don't want to purchase a vehicle which is well below the norm for capacity loss (expect about 10% for a vehicle a couple years old, but you can do better). I'd be looking for capacity above 70kWh (fair) or 73kWh (good) for a vehicle that's a couple years old. For younger 2021 vehicles you have to be more strict; they should show very little capacity loss at this time (many still show maximum rated range indicating capacity exceeding the degradation threshold of 77.8kWh (LR) or ~80.7kWh (P) ).
The range went from 310 miles to 353 miles with all of the upgrades, so yes you want the bigger battery if you can get it.
To be clear, AWD non-P vehicles with the 77.8kWh battery had 353 rated miles (just like the 310-mile version). But later on in 2021, all AWD non-P vehicles seem to have transitioned to "82.1kWh" (usually more like 79-81kWh). So the later 2021 vehicles have more real-world range (though they still show 353 rated miles at full charge when new, for the time being - I guess I expect 2022 vehicles to be announced with a range increase to drive demand - even though (perhaps) nothing will be different (there of course could be other optimizations beyond the pack capacity, like hairpin motor windings or whatever, but what is going to happen there isn't 100% clear at the moment)).
