Return vs. AppleCare
I would always go through Apple service regardless of what you think the timing is - if you think the product needs repairing, the service wing is the best place to get that service and not returns. 

Apple service parts are often of higher quality than the new since some new parts can have manufacturing anomalies and the service parts are tested to a much higher standard - after all, Apple knows that thousands of people are going to get a device that needs exchange immediately (DOA) and they know the service part has to be better than the new in the box experience.

(Also, Apple service is designed to get you service where Apple sales is designed to Make the sale / take your money. Why seek support from the sales floor when that phase of the transaction is concluded?) 

As a class - I’ll take a refurb / repair / known good service part over a new in the box one any day if given the choice. I know refurbished has a bad rep from companies that do a crap job of quality. Apple wants you as a customer for life, so why would they stock the service department with something that won’t make you happy. You’re already bummed you need service and you don’t think Apple hasn’t stacked the deck so they can delight you better from service than new?