This is for 33 GTR's only.. 32 and 34 i don't know as much about differences.... but you could have searched....
Vspec has active LSD which is a bit of a wank, more to go wrong with a pump and stuff with it, plus if you want to change it later to a tighter diff you have to get a non-vspec diff to do the change over....
Vpsec has the faster attesa computer 1/1000th of a second rather than 1/100th... not sure how much difference it would make... i'd guess not a huge amount....
Vspec has stiffer suspension stock.... but most people change suspension anyway...
Brakes, front bar, front lip etc... are all identical between vspec and non-vspec.
As people have said a lot of non vspec have the sticker.. check the rear diff for fins to see if its real.
Personally i'd pick the better condition car...