FWIW, I agree with Metro Red Line's comments 100%. I've debated these same issues several times over the years. My latest variation is considering switching from HO to 3-rail O, due to space concerns and time for modeling in the future. By going up from HO to O, you reduce the 'effective square area' of your layout, by a factor of 4, if my math is right. I have a large space, but limited time and budget to play with. Giving up some scale fidelity, in my case, would allow me to focus on fewer, rather than more space to scenic/detail as I wish.
Scales have continually become smaller and smaller, the latest I am aware of, being T scale at 1:350. When I see what is available in Z scale vs, say only 5 years ago, if I was just starting out, with a desire to model things prototypically, but with very limited space, Z would be a viable option in my book.
Regards,
Otis