Gentlemen,
Which spark plugs are best is a matter of personal preference. Many people feel NGK or AUTOLITE or BOSCH or Champion or even AC are best. Reason: mostly based on personal "feeling" that the car runs better, starts easier, gets better fuel mileage, sounds good, etc. Cost and availability are important issues as well.
Some guys swear by ________ (fill in the blanks) is very much akin which beer is best........domestic vs import vs light vs laugher vs pilsner vs ......
I believe which plug is best is up to the individual based on some trial and error experiences. If sone one recommends say NGK of a certain design, heat range and features and you purchase the recommended brand and type and the result is a damaged engine.....who will be blamed?? Do your own du dilligance. There are many engine variables that effect spark plug selections: compression ratio, spark advance characteristics, fuel distribution, cam selection, operating conditions, final drive ratio, etc. If contemplating a change proceed cautiously.....its far easier to replace a cold fouled plug than to replace "holed" piston or damaged valve. Do not be influenced by price or someone else's opinion.
In my 1970 RS23V0A GTX, l use Champion UJ-11G or Champion HO-8A.....because this is what works for me. In my instance...this is what's best....for me.