I concur with the majority that NGK copper is the best plug for the money. A pencil-thin electrode is probably Iridium-plated. Those should last a very long time.

Any plug that is used as OEM by a manufacturer is going to be a pretty good plug. The requirement for 50,000 emission warrantees has driven plug technology to improve.

The acid test for spark plugs is how well they fire under weak spark conditions. Weak spark can be caused by cranking, corrosion in the primary side of the ignition, or high RPM operation when the coil has little time to saturate (not an issue with a brick). It is also harder for a plug to fire under high compression, full-throttle operation, again not a major problem with a brick. Bottom line here is that bricks are not too picky about spark plugs.

The biggest factor in how well a plug fires under adverse conditions is sharp electrodes. The reason the car always seems to start easier and run better with new plugs is because the edges of the electrodes are nice and sharp. The 'why' has to do with ionizing a conductive path through air, which is an insulator. It is the same reason that lightning rods have sharp points. The use of platinum and iridium plating allows the center electrode to be smaller in diameter, which tends to be better geometry for firing as the miles roll up.

In my mis-spent youth in the early '70s, I discovered that a small block Chevy or Ford with contact points and a single coil could erode the corners off the electrodes of Champion or AC plugs in as little as one day, resulting in a high RPM miss. Then I started racing Japanese motorcycles and discovered NGK and NippoDenso plugs. I put them in my car and never had a problem again.