Index Spark Plug -
There are a lot of claims concerning spark plugs that burn hotter, cleaner, longer and more efficiently according to the design and tip materials used by each manufacturer. I have to admit that my preference is the Bosch Titanium +4 spark plug. Bosch also makes an Iridium and a Platinum Ir Fusion Spark Plug made with intergalactic magic plutonium dust.... They are all advertised to last 100K miles but I've never left any plug alone for that length of time without at least pulling them out for inspection.
Personally I think if the reach, operating temperature and tip materials are all equal, the performance of most any plug will be reasonably on par for most name brands. The PR specialists are probably already typing......
There is one area that does seem to actually make a difference - even if it's difficult for the average person to verify without a bunch of equipment. It is called indexing. You mark the porcelain neck of the spark plug with a magic marker to indicate the orientation of the neg electrode arm. Then install the spark plug to see where the indexing mark winds up. For the best performance the neg electrode should face directly away from the intake valve. If the position of the electrode shields against the incoming fuel charge either a small copper spacer is added (which slightly affects the plug depth/reach?) or the plug is rejected for another one. Of course there is a 97% chance that the plug will be positioned within an acceptable tolerance so it's a minor point for most of us. But it is no secrete that race car drivers are always looking for any hp advantage or edge (no matter how small) and have used indexing for many years.
After determining the spark plug qualities I want and can afford, I then shop for price. Walmart is a great source for equivalent platinum plugs if you can ever get their cotton-picken electronic cross reference machine to work........
Good Luck, Michael
