I found that I got slightly better mileage & a tad better performance in my BBC's by running plugs 2 steps colder than the factory recommendation.
The way it was explained to me, this creates a more even burn across the top of the piston.
The term colder plug and hotter plug refers to how fast or slow the plugs transfers the heat from the tip. A colder plug transfers heat faster while a hotter plug is slower.
The trick is to find a temperature range cool enough to prevent knock and not melt the plug tip, but still hot enough to burn off the carbon and prevent fouling.
The biggest problem in running a colder plug when it isn’t needed, is that it will foul up quickly. This happens because the plug tip doesn’t stay hot enough to burn off the carbon deposits, and so a build up occurs.
Another common problem is that colder plugs can make the car harder to start when it’s cold outside.
This may or not be of any concern when it comes to a computer controlled engine. My experience with plug temps involved an old-school high compression, points & carb, big lumpy cam'd BBC, with the timing advanced to near pre-ignition levels.
Higher cylinder temperatures at the near knock level brings the spark plug firing end temperature closer to the pre-ignition range.
Not sure weather a computer would recognize the slight performance diff between the different temperature plugs & then compensate or not.
It would be interesting to see if there was any advantage or disadvantage.
Anyways, it's always best to err on the side of a colder plug, rather than suffering knock, or even the possibility of blowing a hole in the piston by going too hot.