The larger fish in different areas of the country with a longer growing season are best not compared to our fish.
In a typical scenario those fish are younger and taste better. Age has more to do with it than size, but without a scale sample or extracting an otolith, it is very difficult to determine the age of a particular fish.
All in all, biger fish DO tend to be older, in most cases. But it is not always the case. You might catch a laker that is 20 inches long and thirty years old. I would not want to eat a thirty year old fish!
Stick with pan-sized fish, they are called that for a reason!