It's great to have an indoor setup when the weather gets bad or you just want to quickly run some trains. I bet people have no idea what it takes to keep an outdoor setup running year after year.
I swapped my indoor setup from G scale to O scale 2 rail years ago. It was mainly because I couldn't get the G scale models I wanted. After some time passed, I built another G scale version under the O scale, on the ground. I did that because I missed the G scale running year round inside. (I'm in NY!)