I believe on some cars the SC does some different ECU mapping along with its other functionalities, or something like that. What about on the GT3? If I were to purchase a GT3 without it what exactly would I be missing out on?

 

GT3 adds a wart on the dash and the ability to use the stopwatch...tho it's interface is terrible.

 

So absolutely no performance advantage whatsoever?

In that case I don't care about it. I don't car for its looks and I'd probably put a track-timer in which would be far more informative.

 

Didn't the SC add a sport button to the lower console on the 997.1? I know the 997.2 the Sport button was stand alone, but I thought SC was required if you wanted the sport button for 997.1.

 

all GT3's get the sport button standard regardless of the SC. your statement is true regarding regular 997's