The 'working' bred Labs (i.e. genuine gundogs) tend to be far more leaner and fitter than the show bred or pet ones, which are heavier set and often fatter. Thats not to say the show dogs can't work to the gun if given the opportunity, just that they are bred for looks rather than ability, unlike the working gundogs which are bred for how they perform and not what they look like. Same in a lot of breeds these days, some breeders seem to have forgotten the original function of some breeds.