I would agree with Toff Apple that it depends on the pitch, as that is surely the point of a football ground. If it's extended or reduced by a metre or so, that makes no difference, but if the pitch is realigned, that counts as a new one in my opinion, and I believe Wembley's pitch is at an angle now to what it was at our last (?) visit in 1986.
Each to their own though, and unless we have a competition as to who has been to the most grounds and someone claims a prize on the basis of counting the Buck's Head and New Buck's Head as two separate grounds, you can choose to count what you want, as I am sure people will.
Darlington will be the only new ground for me, although different clubs play at Spennymoor and Hereford since our last visit, so I am very keen to visit all three.