Isn't this interesting... In another forum not much more than a week ago I was the only Bosch Platinum user, and the overall consensus was NGK plugs were great, and there were problems with Bosch Platinum's.
I've used the Bosch for about 10 years in the '73 TR6 and have liked them. Mine get replaced about every 12-18 months because the seal washers get compressed to nothing after 5-6 checks of the plug color. This year's been rougher - don't ask.
So - I decided to give the coveted NGK's a try, sorta. Why try a standard plug? I put in the "V" type a week ago to test 'em. BP6EY. Right away I noticed a change in the exhaust "note". Not as loud, but more even. Yep - very subjective.
I went with the "V" type because according to NGK the spark is always on the outside of the gap so ignition of the "charge" is better. Other reason; we do things electronically to improve ignition - MSD or XR-3000 with sports coil. This may be a physical addition to those electronic improvements.
I've been working on mileage the past month. Couldn't get above 20 mpg. First pass at mileage now is 21.6. Still low, but an 8% improvement. I won't give that all to the plugs, though - too early.
The car's performance does "feel" better. Again - subjective.
The Bosch plugs are not supposed to be gapped - you put them in as is. I've always opened them up (as with the NGK's) to 0.037 - 0.038". That could be a difference I'm responsible for.
Anyway - if your list is low, try out the BP6EY's.