In order to 'do the math' on this one, you would need a list of all the opponent types in the game, with their numbers, level and base experience values. The type, number and level info could probably be pulled from the data.000 file of a new game, but I'm not sure if the experience points are stored there as well.
Neglecting quests, you could then calculate what the effect would be of defeating the strongest opponents first, clearing particular areas first, etc.
Of course, when I say 'you' above, what I mean is 'not me'.
I am a little curious about this now, but don't see having the time for it.