I don't think it really makes a difference. Do you generally see more of one species than the other? Living in Minnesota our BW Teal take off at the 1st sign of cold weather so most of the season we get GW Teal. Personally I would go with GW decoys but in your state it may be the opposite. I don't even know that putting out Teal decoys even makes much of a difference. If I have a small group of Teal decoys off to the side of my Mallards then the Teal will usually try to land by them but they still come in if I have Teal decoys or not.