I am working on a circle/oval/loop (or whatever you like calling it) double main line with one side against wall layout, that I have switched from operating from middle to outside and back and forth at least twice. The middle seems ideal but locks you into a spot. When operating multiple trains, the lift up or drop in access bridges are great, but I am getting older and slower to pass thru them and then pass back out, without stopping the trains.
It could be different for everyone, but for me, the operating spot is best outside the loop. Just my opinion, and it changes periodically.
