Trying to decide between 2017 and 2018 Prime

Doubt much difference between a three and four year old car everything else being equal.

 

Not sure what rebates are offered in your region, but have you priced new PRIME? In our area, a brand new 2021 PP LE can be had ~$18k after full tax credit.

If buying used, 2018 may still have a warranty left if it is less than 3yrs/36k. Otherwise, I don't see too many differences in those two model years. In general, for the traction battery, the age is more important than the miles, but for the engine and any other moving parts, miles are more of the factor than age.