You always want to buy the newest Tesla you can comfortably afford as the hardware often changes on these vehicles. As some have already pointed out, the most important is the new/fresh battery pack & warranty which outweigh everything else. The battery is the most expensive component and basically the heart of the vehicle. The newer car should also be better built, with a more comfortable suspension, a significantly faster infotainment system for media & internet apps, and probably includes the best all-season tires you can buy = the Michelin Pilot Sport AS4.
Unless you are very familiar with FSD, there's also a huge chance it doesn't do what you think it does. At best its strongest feature is automatic lane changes which will help immensely with using AutoPilot on longer drives. At worst it's a suite of features that are mostly gimmicks to use once to show off to friends and family. With the FSD beta now open to all who purchased it, its possible the vehicle can be used with that.. but it is a very hands-on experience that requires your strict & undivided attention.. and should be viewed as driver-assistance software only. As someone else has suggested its best to buy the $199 monthly subscription to FSD to see what features will truly appeal to you. And once you understand exactly what you are getting, determine if it's worth the premium price.
