I really have no opinion. Ive never had one fail. Recently I thought I did , but it turned out to be a bit of green and black in the plug, once cleaned they all worked fine. I have a dino, and actually ran all three to see if there was any difference. Heres what I found.
Black ( still available at some international dealers by the way)(I recently bought 3 black from the dealer near me, cleaned them out. lol) This CPS was my favorite. It made the most hp. That was the only reason.
Grey Made the same hp as the black, but idled rougher, and was noisier during acceleration. Noticeably.
Blue (Looks purple to me) This one made the least hp, but ran real real smooth and quiet. And I got better fuel economy. I run this one now, just because of how smooth it is, and economy. Acceleration is smooth and steady power curve.
If Im racing, which I do a lot with this bad boy, I use the grey. It makes the same hp as the black, but the curve is much raunchier, and it does a bit better on the 1/4 mile. Seems to light up quicker with this one. The dino curve is steeper, and levels out a bit sooner, explaining the 1/4 mile times.
Blacks are my spares, which I have never needed, touch wood.
Up here, ford seems to only sell the purple(blue), International has grey, or if your lucky the original black.
Not sure what others sell.
Not really solid data, as my motor is really built up, stock may show different. But those were my observations during dino runs.
2002 F350 Super Duty, Crew Cab,Long box,4x4, 7.3 PSD, Complete rebuild .010 over by myself except balancing, 2000hp billet connecting rods, ARP main and head studs, ceramic coated pistons, Smith Bros Chrome Molly push rods, Comp Cams springs, shims and seals. Competion complete valve set and head grinding and vacuum tested, Adrenaline HPOP, DP Tuner Infinity DX programmer and full load of tunes modified for my new Stage 3 250 shot injectors, ceramic coated exhaust manifolds and up pipes and collector, BD Diesel triple clutch furnace brazed billet torque converter and BD pro engine brake and compressor set up, MBRP 4" stainless turbo back, Driven Diesel regulated fuel return system, AFE pro stage 2 cool air intake, riffraff billet Whicked Wheel 2 compressor wheel in a GTP38R turbo, riffraff blue cooler boot kit and coil clamps, International Double Ceramic Coated Bellowed Up Pipes
1999 Mustang GT Convertible Anniversary, rare stock electric green
2009 40' Raptor Velocity Toy Hauler