Interesting question.
Rush has only averaged 30 mpg in one season (2009-2010). From 2008 thru 20111 (excluding last year for injury) he averaged 26.75 mpg and averaged up to 10ppg, 4rpg and 1 asp. Career 41% 3 pt shooter. So there are some areas that he will be better (3 pt shooting) than Burks and some that Burks will be better (assists). Not sure comparing them is the way to go.
You figure that there are 96 mpg to average out amoung the wings for each game. Say 30 Hayward, 30 Burks, 20 Jefferson and 16 Rush? That leaves harris in the cold. Do we want to rob him of time given his effort and D? Tough decision. For me Williams looks like the odd man out in that equation but he has merit as well.
Once Rush has his rust knocked off and is in full swing those minutes could be re-evaluated. That will also give Burks at least 2-3 months to show what he can do with extended minutes.