I thought "new car smell" comes in a can and they use it to refresh the experience in an older car? Is it possible a 4 year old car would still have it, left to its own natural decay?Depends on if you care about the trim level options.
Brand new is nice, but if the 2017 is in excellent shape then I would go for that personally.
I bought my 2016 this June as a dealer CPO and it still had new car smell it was in such good condition. The cost savings to go with a slightly older car was worth it to me.