On a style note, I prefer the 2016 and newer. I believe CUE is far more responsive in 2016+ as well, although the screen can still crack/delaminate/whatever (I got a small crack in mine, still under warranty fortunately). I greatly prefer the 2016+ grille. But if you have a great deal on a 2015, with evidence of regular oil changes, then good for you. My car has been low maintenance compared to my LS430. no timing belt, no brake pads needed yet at almost 6 years/63k miles. Just oil every 6-7k as indicated, coolant at 5 years, transmission fluid at 45k since I got car used at 25k, brake fluid every 3 years. And 1 dead battery at < 4 years (warranty covered!). No other mechanical repairs (yet...).
Shocks damaged in bad pothole were exorbitant at dealer ... $1200 for one, not even a pair!!! I was robbed. Magnetic ride control shocks are relatively pricey even at an independent, so make sure they are in good shape or that will be a sizable bill. Twice car has started "wrong" with hesitation and check engine light and unable to go above 20 mph. A restart fixed immediately both times. Headlights are poor IMO -- others disagree. Good, decent car overall. Some love it. I like it... it has grown on me. Find the engine a bit gruff but rest of car is quiet. I did not like original tires, currently have Vredestein Quattrac Pros. Many others dislike original tires for noise/wear... make sure you like the ride and noise on various roads.
Finally, some claim 20" tires are worse-riding and platinum-trim wheels degrade due to 2 metals... If you are getting premium with 20s or platinum trim, check out ride and wheel "health" (on the Platinum) for corrosion, etc.
Good luck.