Diamond rackets
Weight sits high in the head. That is the whole story: the mass is furthest from your hand at the moment of contact, so the smash leaves faster than from any other shape.
The trade is real. The sweet spot is the smallest of the three, off-center hits feel dead, and the frame is slower to swing when someone drills a ball at your body. A diamond rewards a player who already times the ball well and punishes one who does not.
Buy a diamond if you finish points from the net and your arm is used to the load. Skip it if you are still learning where the middle of the face is.