Are you sure commissioned will always do better?
About a decade ago I was in a group that investigated incentive pay theory with the goal of making a recommendation. I read two books and maybe 40 journal articles on incentive pay. The overall consensus is that working on commission (or similar practices) works well in some situations, but overall brings more negatives to the business than positives. One theorist said "It only works in buffalo hunting and shoe selling."
One of the biggest drawbacks is that in a company which functions best when employees work cooperatively with one another, it destroys the needed cooperation. The employee who makes the big bucks could be achieving those big bucks in ways that are great for him or her but harmful to the overall success of the company.