I disagree, but setting aside the radius/diameter debate, consider the simple equation: area=pir^2. How is it not more difficult to think of the constant in terms of diameter, when the rest of your equation is in terms of the radius. Unless you use area = 1/4pi*d^2, which I have never seen.
I'm not telling you what to do, I'm telling you what I like to do. Yes, I do sometimes use (pi * d^2)/4. It's not more efficient, and I didn't claim it was (though if I were concerned with efficiency I could argue that pi * d is a pleasingly simple way to calculate circumference).
I'm sorry that my personal idiosyncrasy bothers you so much.
