From what I've heard and seen the 2016 offers a low gain mode, and the gain overall is less compressed and brighter. I'm already running my 2015 with the bass up, I don't want the amp any brighter so I'll be sticking with my late 2015 the way it is.
I have a '14 BE, and have ZERO interest in sending it in for updates. Sounds great. I also like the fact that mine will sound different then the new ones that flood the market. I prefer early JCM 800's as well...