What causes the difference between Maine and Canadian lobsters? In a first-season episode of the US TV show Kitchen Nightmares, the well-known chef Gordon Ramsay states that there's a "big difference [in] taste and flavor" between Maine lobsters and Canadian lobsters.  He gets into an argument about it with a restaurant owner who claims that they're really no different.  (If you're in the US, there's free video of the argument in question here, from hulu; start at about 16:33.)

Admittedly, I don't know whether Maine lobstering waters and Canadian lobstering waters border each other, though Maine waters and Canadian waters certainly do.  And Gordon Ramsay owns more Michelin stars than I own plates, so he's clearly the expert.  But I also find it hard to dismiss the owner's points &#8212; if they're true &#8212; that both lobster types are the same species (Homarus americanus), and come from the same North Atlantic waters.

So, what is the cause of the difference in taste/flavor/quality between Maine lobsters and Canadian lobsters?
First of all, Ramsay was primarily concerned that they were advertising Maine Lobsters and selling Nova Scotia Lobsters.  He actually didn't comment on the flavour.  

I've searched about 20 web pages (nothing authoritative) and the consensus is that the colder the water, the better the lobster.  

But, the waters off of Maine are fed by the Labrador current, which is the same water that flows past New Brunswick, PEI and Nova Scotia.

If there is a temperature difference, it is likely not very significant, and any effect it would have on flavour is minimal at best.