>> comparing 3 rail O to S that while, yes - S is smaller, the turning radii are not all that much different.
True or not true?
If building a layout is in your future, the radius of the track is of minor consequence compared to the size of structures. Compare the actual square footage needed for a large passenger station between O and S. Most O layouts cannot accommodate a properly-sized large structure -- like a roundhouse with more than two or three stalls. With S, many large structures can be fitted into the available space much easier.
In addition, the appearance of two-rail track beats the 3-rail stuff hands down. And, the similarity of track radius does not address the issue of realism. An S train on 20" radius curves looks a heckuva lot more realistic than an O train on 16" radius curves.
If minimum radius is your goal, perhaps HO trains would be a better choice. N scale goes down to 9" radii. Food for thought....
Just contemplating.......Ed L.