$27K is absurd. I paid a little over $22K out the door for my 16 Touring. Are you looking into tech package? Looks like the dealership is looking for fools and trying to unload the last of their 15s. I wouldn't pay over $20K at this point for a '15 since there are so many 16s and in my opinion are much better than 15s.
Better navi - 16 uses Navteq vs TomTom on 15, and even if your car doesn't come equipped with navi, its just a $200 SD card from ebay away from being equipped..
Better interior
Better resale value, you get an extra year + midcycle refresh models always carry higher resale
And I noticed the NVH is improved on the 16s when I drove 15 and 16 back to back. Others stated they didn't notice any difference.
I think you should go drive them both and pick the one you really like, then have the dealership sharpen their pencils for a price. Where do you live?