Delta is more efficient for cooling than Nidec: 600rpm less fan speed & 5db less noise level to maintain the same PS4 Pro CPU temperature 47 degrees in RDR2 game. But Delta Fan has high frequency noise peak at 1141Hz that can be annoying for some people. Delta: for those who want less noise overall and OK with 1141Hz high frequency Nidec: for those who annoyed with high frequency noise, want stable noise sound even with higher level of noise overall Nidec: 19 blades, , 1200rpm base speed in Homebrew Delta: 23 blades, , 900rpm base speed in Homebrew Test performed on both CUH-7216b consoles, same PSU model, same fresh thermal paste PTM7950 applied, PS4 Temperature app set to 47 degrees, run RDR2 game.