Good question. Up until recently I thought the proposal conversion rate belonged to Sales and therefore Sales performance should be based, in part, on the rate of proposal wins.
After attending a FunnelAcademy(tm) workshop lead by Hugh MacFarlane, I have changed my way of thinking.
The percent of proposals won is directly related to the quality of the buyers that marketing places into the revenue funnel and advances through the early stages of the funnel.
Yes, Sales should still be measured, in part, on their effectiveness in closing deals, but so should Marketing.
What better way to put Markeing and Sales on the same page than to have both evaluated for the same key business metric?