Next gen seats should be the 3rd generation seats, they were built by Recaro and are supposedly more comfortable than 2nd generation seats. Since these seats were introduced in Aug 2016, I am fairly sure the 2014 has the 2nd gen seats. Watch this
video to hear about gen 2 seats, jump to 2:15 to see gen 3 seats. It's pretty easy to spot the differences between the 2 seats, and I don't believe the gen 2 seats had an adjustable headrest. The wiki notes that:
On August 23, 2016 the newly announced P100D and P90D have a new seating choice called Premium Seats which are offered in White, Tan and Black leather. The previous Next Gen seats were dropped as an interior design choice for the P100D and P90D. The new Premium Seats offer a prosterior cooling feature with air flow capability as well as adjustable headrests.
The advantages of the center console (
pics) is the interior adjustable cup holders, the rear USB ports (introduced in Sept 2016 per
wiki), and the rear seat cupholders. The rotating phone dock that hides the two USB ports and 12V outlet is fairly useless. Most phones with a case won't fit in the dock and the plastic pieces that hold the phone in place are not sized for newer (larger) phones. Disadvantage of center console is that you lose the open feel of the front compartment.
One advantage of the center console compartment is that it will easily holds large (30oz/YETI) cups because the compartment dividers are adjustable. You cannot fully insert two 30oz cups in the armrest cupholders due to the width of the cup at the top. Wrt the USB ports, I opted to retrofit the rear usb ports into the console by following instructions this
post. I have all the part numbers if you want to add this later.
Here's a
thread discussing + suspension. Just depends on your driving, not sure if this would be valuable to you or not. Now that the Raven suspension is available on newer models, I am guessing that devalues the + suspension.
To summarize, I would go with the 2016 if it has the 3rd generation seats (bonus if it has the center console). If the 2016 has the same seats as the 2014, I'd go with the 2014 and (if important), retrofit the console. Adding the center console is a job you can do in a half day, PM me if you want the full parts list.