short reach or long reach sparking plugs

hi everyone    i have for a number of years used short reach sparking plugs. speaking to someone about 15 years ago said champion d21    new equivalent mgk ab6   the book says klg long reach so what are your thought. ps what do you think klg stands for   i will buy you a pint of the black stuff if ytou are correct. ps i have had no problems running on short reach. 

First off, for my pint: KENELM LEE GUINESS, the name behind KLG.
Secondly, I recommend a look at my website entry "How Long is Your Reach?", written many years ago as a chapter of "Learn Your ABC", a series of seven articles for the VMCC Journal. 
It appears under "Articles", somewhere in "Tech.Tips".