Have agree with Robert on this one, that second plan looks very "train-set!"
My priority would be to make the double loop as long as possible. So providing the room is just for your layout, I would build the loop around the outside of walls. If you did this you could make each basboard up to 2 feet wide if you wanted to and still have a large operating well in the middle. You can build in a lift-up or removable section for the door to open, or alter the door to open outwards.If you can get away with it you could even remove the door altogether! (don't laugh)