..........O is too big for inside running.
All the scales have gotten crazy expensive.
If that's really true (probably not as you can make any scale as expensive as you choose...) then it's not a factor in deciding what scale to pursue.
I've always felt like S was the "right" size but I've been concerned about the viability of it - given lack of manufacturers.
Then you make what you want while scouring the planet for what's been made.....same as in any other scale....and have fun doing it.