Basically the posh plugs will last longer and operate more efficiently for longer .. but if your ignition system is in good nick and you clean/adjust your plugs once a year, you won't feel hardly any improvement over "normal" plugs.
The NGK spark plug naming convention describes the plug;
B = 14mm thread ("D" is the smaller 10mm plug)
P = Projecting nose electrode... (no "P" is a regular plug)
R = Resistor plug (for suppression of electronic interference from the ignition system)
6 = Heat rating. NGK uses a high number for a "cold" plug.. (cold plug is one that can take higher engine temp before melting.. so for hot summer track day, use a "7"... for a lot of city driving at -30C, use a 5. Too big a number/too cold a plug will foul up.
Confusingly, Champion use a small number for a "cold" plug.. so a CN6 can take more high temp abuse than a CN7. CN7 is the same as and NGK 6. CN6 is the same as NGK's 7, CN5 is the same as NGK's 8... etc.
E (or A or C) = relate to the construction of the plug and not its performance, so don't worry about these
G (maybe "P" now) = Platinum coated central electrode
I = Iridium
V = V-groove cut into the inside of the outer electrode. The central electrode will probably be platinum and very thin (like a needle).
At the moment I'm using Champioon Iridium plugs.. mostly because the rear plugs on the v6 are a bit of a barst to check, so I want plugs that are more maintenance free.. but in terms of performance they're no different to any regular NGK or Champion od Bosch plugs I've used.