Hello, I was responding to a post in r/TeslaModel3 about my thoughts on my new 2018, and as someone who has been extremely plugged into the used market for M3s <40k, I wanted to make a post to help anyone on a budget.
Model 3s have amazing batteries and have used the same tech since launch. The only upgrade that really matters and you would not be able to get, is the heat pump, but if you get a Long or Mid Range RWD, you will get at least the same range as a 2021 SR+. Because of this, I would not recommend the 2019 SR+, I do think you will miss the extra range. Definitely would prefer a 2018 Mid Range w/ 40k miles over a 2019-20 SR+ with 20k (seem to be a worthy price comparison). The Mid-Range has a larger battery, has a higher peak charging speed (200 vs 170 kW) and does not slow down its charging as fast as the SR+. Same goes for the LR RWD but better.
Then, I would say the power trunk and cosmetic upgrades are surely things I would like, but are luxuries, and you can add things you can do yourself. Any other color I would probably chrome delete, but I personally think it looks great on the black so I am keeping it (if I tint my windows I will black out, but that’s down the road).
I think the decision to buy used or new should come down to if you want either a LR RWD, which they do not sell anymore, or a FSD package. If you do not want either, I would say the 2021 SR+ is the better option, but otherwise, I would very highly recommend the LR RWD and Mid range regardless of year.
EDIT: What I ended up going with, was a Black 2018 Mid-Range RWD with FSD, aero wheels and a White interior. It had 42,000 miles on it, and cost $36,900.
Hope this helps someone get their dream car!