I have only recently become interested in oysters. I started unaffected by the craze, then slowly started to like them, a few months ago started to crave them, and only about 6 weeks ago decided to really learn about them. My favorite I would have to say are the Duxbury. The cold water there makes for a sweet morsel of an oyster and whatever marine life is in the bay gives it a clean, almost cucumber-like aftertaste (I am sure there is a term for this, so oyster connoisseurs please forgive me). My second favorite would be Wellfleet, however unlike the Duxbury, they have a shallower cup (thus less "meat").
With our recent trip to the Cape, I had the pleasure of frequenting Lamberts Seafood Market and found they only had one variety of oysters. Husband and I asked for two to be shucked on the spot, and agreed, these were better then Duxbury. I came back a few nights throughout the week for pick up a few dozen of the Dennis oysters. Clean, briny, but not overly salty, with a sweet, almost lobster-like aftertaste. I definite winner! Next time I'll remember to bring a shucking knife, instead of using a shrimp deveiner, so I retain all 10 fingers.