Normally I sight in on a bench, and then practice from shooting sticks and trees. Although in my one blind, I have a window exactly to the height of my shooting sticks. So I use both the window ledge and the sticks and that is really an accurate way to shoot.
The reason I also practice from leaning on trees is.. when I walk around, that is normally how I will end up shooting. There really is not all that much difference I find from shooting with sticks and trees as a bench. Do you find a large degree of difference?