Spark plug NGK or OEM BMW

Iridium, tried and proven. Ruthenium looks like is an experiment by Ngk, I would give ti some time before these plugs prove themselves reliable before buying.

Another plug to give a try if you want to stay stock heat range - NGK's Ruthenium plugs LFER7BHX . Call it a placebo effect but after install cold start idle sure felt smoother and after 4000 miles they're running as good today as day one, gas mileage has been pretty good as well around 31 mpg +-1mpg @ 75mph. No cold start misfires. Overall a pretty solid plug for this engine and it's reasonably priced.

Brisks are throwaways that need regular attention by either regapping them every few thousand miles or replacing. You can run NGK 7437-9s for 20k in a stage 2 car without touching them. There's a big price difference so you get what you pay for.

Did my plugs 4 months ago with NGKand they still feel great.

I run NGK BKR6E's in my rabbit. I have had the best results and longest life from the NGK plugs. To the point that is all I run in any of my cars! LOVE them!

If you have a bike that fouls plugs easily, particularly with condensation, the pointy electodes of an irridium plug will still spark. My XV535 would get regular plugs wet with fuel and condensation in winter and then refuse to start. Started reliably on iridium.

I personally run NGK without any issues.

these work fantastic.

New NGK plugs were a definite improvement. MSD coils were not!

I've tried NGK's gaped at .28 twice now once as preventative maint. and again some 20k down the road out of curiosity and both times i'd miss under WOT.