I've always put the rope on the downhill hip, but recently I've seen a couple references recommend putting the rope on the uphill hip. The reason being that if someone behind you falls, it will spin you into the slope which is where you want to be for arresting. The downside is more chances to step on the rope and get tangled up while climbing especially if any slack gets in the rope.
Maybe it just comes down to personal preference, but I wanted to see what other people think.