I shot Thunderheads and Wasp Hammer SSTs exclusively till this year, and they both shot equally well. I decided to try the NAP XP Spitfires this year, since I have never had that great of a blood trail with fixed blade heads. I shot a doe last week with them as a trial for them, and I won't be switching back to fixed heads. I had an instant bloodtrail, and the doe bled completely out in the 80 yards or so she ran before piling up.