They both make fine keychain ornaments and hurt when you wing them at people. I saw a picture of someone who covered heir desk with them and placed a glass top over it. That looked pretty cool.
Hard to imagine anyone actually wanting to *use* either one. But if I had to... The P4 will run a little cooler than the D. I suppose that's worth something.
But seriously - It's like having to choose either the droppings from a Malamute or a Malinois. What are we supposed to do? Count which draws more flies? Check the 'crust' for proper consistancy? Sorry - They're both sh*t, and I wouldn't consider using either at all.