Originally Posted by AGHRMatt:
there's really no big advantage to 3-rail over 2-rail save the absence of reverse loop/wye issues.
Actually, THIS alludes to what I consider the primary advantage of O2R over O3R...the potential to use DCC. In doing so, there are electronic switching devices that automatically make polarity changes in the trackwork as a train moves through a reverse loop or a wye.
But that's just the tip of the 'berg' as far as I'm concerned. Having standards to which the entire manufacturing industry subscribes and participates in when it comes to a command control system is, far, far and away the BIG ENCHILADA of O2R. This incessant bickering and wasted spending on incremental digital control improvements between the O3R sumo's...many, if not most, of which 'improvements' (
) put your past investments into the proverbial dumper, and/or justify higher and higher prices of the basic motive power...is just plain, well, ...STUPID!
Which is THE reason why I have never embraced the miasma of O3R command control systems. But, of course, that's just MHO.
My how nice it would be to have the O3R industry leaders be able to offer ALL of their motive power simply as "DCC ready", let the current, well-established, happily-providing DCC industry provide the elements of the standardized control/sound systems, and spend their investment resources/cash/time on dies/tooling/finishing of new products...locos, cars, trackwork, accessories, etc..
"Selling all of my PS1 engines...going to PS2.0!" (Ka-ching)
"Selling all of my TMCC engines...going to Legacy!" (Ka-ching)
"Selling all of my DCS engines...going to TMCC/Legacy!" (Ka-ching)
"Selling all of my conventional engines...going to Lega-Proto Commandimonium!" (Ka-ching)
Selling all of my O2R 'conventional' engines...going to DCC O2R engines. 
NOT!
(sigh)