There have been many cases for example in the Mediterranean where Turkish F-16s engaged in mock dogfights with Greek F-16s. Sometimes the Turkish Vipers "won" sometimes the Greek Vipers "won". It depends greatly on pilot training, morale (in times of actual war) and also on aircraft capability if they have different Viper versions. If for example you take equally skilled pilots and put one in a Block 60 and one in a Block 5/15, in a dogfight the Block 5/15 will probably have the Block 60 for breakfast as it is much lighter and much more maneuverable. But in BVR the Block 5/15 will be easily dead by the Block 60.