Nearest the door, here's why:
The urinal nearest the door (depending on the layout) may require actually walking back toward the entrance wall. Bathroom doors open inward typically, and so the bathroom door is often in the way of walking straight to the urinal by the door - which makes it awkward to get to and often for that reason (and for others) the first urinal is the least popular.
Least popular means good for me for two reasons. First, I'm less likely to have someone standing next to me. Second, the one used the fewest times has the least amount of germs on the handle and elsewere. Urinal number 5 is one that has been abused by everybody who walks into the room. Number 1 is just as private (can't get sandwiched between two guys) but less popular typically.
Really the only two urinals that one can choose in this situation are the ones on the ends (don't want to be sandwiched). I just think that the least popular of those is best and its obvious from the urinals I frequent, that the first one is unpopular.