There ae a few differences between the 15's and the 14's, mostly cosmetic. The shower heads are different, the 15 has an aerating shower head. There is a solid surface counter in the bathroom vanity with an undermount sink in the 15, not like that in the 14's and earlier. There is a change in the location of the keyless entry on the coach door, I cannot confirm if the manufacturer changed but the location definitely changed from the door to the door handle. There is a new paint scheme for 15. The TV cabinet has been changed and the location of some of the TV switches...beyond these things, I have not noticed any difference, other than the price increase.
2014 Seneca 37FS, 2012 Mazda2 on a Master Tow dolly