I had "American" labs back when I had them, a buddy currently has "British" labs.
The most marked difference I see is in their behavior. My buddy's dogs appear to be much more laid back and quiet while American dogs were much noisier and rambunctious. Much of this may be due to American dogs often being kenneled outside compared to the Brit dogs I've seen. When the dog is next to you, it is much easier to correct it for excessive barking or jumping.
On the same line, the Brits seem to respond better to a gentler touch when training. If one is used to training Goldens, then I think they have the correct mindset for Brits. American lines have developed to handle a lot of pressure when training. That can be handy when one makes a mistake but the dogs seem to test the handler more often. One type is not better than the other, it just means one needs to pick a line that best meets the handler's personality and style.
Body wise, the Brit lines seem shorter and stockier. That makes sense as the breed is used more as a retriever than flusher like here in the States. American lines run more of a gamut of body types of which I preferred the taller and ranger body.
Needless to say, these are some very general observations between the two versions. One still needs to research the breeder to determine if their pup will likely be a good match for you.
This idea about the hard temperament of American Hunting stock is dated. The force fetch has fallen out of fashion. You’ll find in the newest generations of American Labs, a dog bred to hunt hard with athleticism, instinct, drive and discipline, and a dog bred to be a companion and live inside with it’s people.
