Re-opening this long dead thread. Enough scans have been submitted since Billy's initial query to conclude that the variations are home jerseys and away jerseys. I have no idea if one is more common than the other.
In most cases here the home version has been arbitrarily assigned number XXa and the away version XXb, but in a few cases it is reversed. Would I screw anything up if I adjusted some card numbers to apply the more common convention across the board?
Also, can anyone confirm that the base set and the gold parallel have all the same variations? Some are only listed for the base set and some are only listed for the gold edition. I just added a Tony Parker home variant to the gold checklist because I am holding one in my hand, but I am hesitant to blindly copy cards from the base checklist to gold checklist and vice versa without visual proof that each such card exists.