If you buy used from Tesla, I think it comes with an additional 1 year 10k warranty after the existing one expires. Also, any advertised features (FSD, EAP, etc) will be on the car; you won't have to worry about them getting pulled unexpectedly.
The disadvantage is not being able to test drive the car. You might be able to see it if it's local. I've done that before. If the Tesla salesman is nice they might allow you to sit in it, but no guarantees. If you buy sight unseen, you get what you get. You might be able to convince the service center that certain dings/scratches don't meet their standards and have them repaired, but that's also no guarantee.