... just to add, in my opinon , both boards have similar bottom end and its hard to tell them apart in that department unless you can be aggressive with the kite,,,, then the newer one has a little trick up its sleeve.
To explain, I find the newer '14 version is better at holding an edge and as others have already said here, tracks better, especially when powered. If you use your kite aggressively in the lighter winds you get power spikes as the kite dives or climbs and if you can edge against it during the power spikes, translates to forward board speed. Keep sining the kite using all the apparent wind to further assist you. If you don't use the boards edge abilities as effectively then you rely upon surface area, fin drive, kite size etc etc. and your forced to either head downwind a bit or run out of oomph.
I lent my 5'5" to a few friends who don't ride surfboards often and love TT only say the '14 Nugget is better, asked them why and they all say you can edge them better than the old one.