Good info. I really only on drive the truck on long trips and tow often with it. Either that or I drive it following the old Italian tune up adage. Colder is probably good for me. Plus I run a 93 tow/perf tune as well.The type of driving also is a key factor. If a lot of your driving is City Traffic with stop & go, then you would prefer to us the stock plug.
But if you do a lot of hard driving, highway or towing; the colder plugs would be better.
I have ran both (stock & colder). I do a lot of City Driving; so I usually run the stock plug's heat rating to avoid fouling.