Tim, to answer your question ..
The general thinking today and the results that I've personally seen on plates would indicate that the actual choke constriction has much more to do with the pattern than the length of the choke itself. It has been a topic of conversation/discussion for at least a hundred years & I expect the jury will remain 'out' on this subject for at least another century, and then come in 'hung'.
As many never get around to patterning their guns, it is oft more a question of how the user perceives the issue anyway.
If you will look around, you can find some published comparisons of Beretta 390 type guns tested with standard 'short' choke tubes and virtually a myriad of after market longer or 'extended' ones. Similar constrictions generally produce similar percentages, all other things being equal.
