If I had one choice I'd say NGK, Bosch are good as well. AC's are more readily available and cheaper, but don't last as long. I developed a disliking of Champion plugs in the 70's, could put a fresh set in the Camaro, and by 1500 miles it would develop a miss. Of course these were the pre-electronic ignition days, that might be part of the issue. I like center gap plugs for 2-strokes. All the plug hype with multi electrodes and such might make a difference with high performance applications, but I've never seen a difference in most cases. I've been running ngk iridium's in the CVZ with good results. More important is to purchase a quality plug, and don't be afraid to take a look at them every now and then. The plugs tell a story about what's going on inside the combustion chamber, listen to what they tell you. Plenty of guides out there, find a good one, print it, hang it on your shop wall. Good luck.