Yes, it does make a difference which is which.
Dog breeding is all about refining characteristics which appear in the parents and is aimed towards a certain goal.
Show Labradors are bred to improve and refine the parents characteristics and are aimed at perfectly matching the breed standard physically, and conforming most closely to whichever physical appearance is currently in vogue with the judges and showing community. Currently a hefty, shorter legged, wide chested look.
Working labs are bred to improve and refine the parents characteristics in the same way, but the goal here is to further improve the dogs stamina, bidability, game finding ability, nose, braveness and so on. The aim is to make the dog best able to do the work a lab is traditionally used for.
Therefore, a show breeder wouldn't be concentrating on refining skills - just looks and while the drive to retrieve is still there, because it isn't being refined, it can often be rather deeply buried. That's obviously not to say that a show dog can't work - rather that he might be a bit reluctant to do so.
That ties in with the kennel club fit for function campaign - that all dogs should be physically capable of doing what they were originally bred for and sadly, IMO, there are a whole lot of labs out there who just couldn't do that.
The same goes for working bred dogs though - they're often bred without reference to looks, so trial bred dogs (the pinnacle or competitive side of the sport) and therefore some working dogs can be a quite snipey and very slight.
It doesn't just apply to labs, obviously, the difference in breeding emphasis. The difference between a show cocker and a working cocker is enormous!