I've run both NGK BPR-9ES and the Champion equivalent that Polaris specs as OEM. The Champions seem to burn cleaner. Somewhere I have pics of NGKs next to Champions after a day of running on each, and the Champions are noticably cleaner. I run Champions when I find them, but it seems more places carry NGKs. NGKs work, but may as well run the plug that the ignition system is engineered for (or the plug that was engineered for that ignition? what came first chicken or the egg). The difference is slight, but it is there.